Filed Pursuant to Rule 424(b)(5)
Registration No.333-124921

SUBJECT TO COMPLETION

Preliminary Prospectus Supplement dated February 27, 2007

PROSPECTUS SUPPLEMENT

(To prospectus dated August 4, 2005)

$                                             

$        % Notes due 2013

$        % Notes due 2017

        We will pay interest on the notes on                     and of each year, beginning                     , 2007. The      % notes due 2013, which we refer to as the “2013 notes,” will mature on                     , 2013, and the      % notes due 2017, which we refer to as the “2017 notes,” will mature on                     , 2017. We may redeem either series of notes in whole or in part at any time at the redemption prices set forth under “Description of Notes — Optional Redemption.” If we experience a change of control triggering event, we may be required to offer to purchase the notes from holders. See “Description of Notes — Change of Control.”

      The notes will be unsecured obligations and rank equally with our existing and future unsecured senior indebtedness. The notes will be issued only in registered book-entry form and in denominations of $1,000 and integral multiples of $1,000 thereafter.

     Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

      The notes will be ready for delivery in book-entry form only through The Depository Trust Company on or about                     , 2007.

Joint Book-Running Managers

The date of this prospectus supplement is February , 2007.

TABLE OF CONTENTS

ABOUT THIS PROSPECTUS SUPPLEMENT

      This document is in two parts. The first is this prospectus supplement, which describes the specific terms of this offering, the notes and matters relating to us and our financial performance and condition. The second part, the accompanying prospectus, gives more general information, some of which does not apply to this offering. If the description of this offering and the notes varies between this prospectus supplement and the accompanying prospectus, you should rely on the information in this prospectus supplement.

      In various places in this prospectus supplement and the accompanying prospectus, we refer you to sections of other documents for additional information by indicating the caption heading of the other sections. All cross-references in this prospectus supplement are to captions contained in this prospectus supplement and not in the accompanying prospectus, unless otherwise indicated.

FORWARD-LOOKING STATEMENTS

      This prospectus supplement may include “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”) and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Statements containing words such as “believes,” “expects,” “anticipates,” “may,” “will,” “should,” “seeks,” “approximately,” “intends,” “plans” or “estimates,” or the negative of these words, or other comparable terminology. The discussion of financial trends, strategy, plans or intentions may also include forward-looking statements. Forward-looking statements involve risks and uncertainties that could cause actual results to differ materially from those projected. The most significant of these risks and uncertainties are described in our Form 10-K, Form 10-Q and Form 8-K reports filed with the Securities and Exchange Commission (the “SEC”).

      You should carefully read this prospectus supplement, the accompanying prospectus and the documents incorporated by reference in their entirety. They contain information that you should consider when making your investment decision.

      You should rely only on the information contained or incorporated by reference into this prospectus supplement and the accompanying prospectus. We have not, and the underwriters have not, authorized any other person, including any dealer, salesperson or other individual, to provide you with different information or to make any representations other than those contained in this prospectus supplement and the accompanying prospectus. If anyone provides you with additional, different or inconsistent information, you should not rely on it. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference is accurate only as of their respective dates. We undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates.

      This prospectus supplement and the accompanying prospectus do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the securities to which they relate or an offer to sell or the solicitation of an offer to buy such securities in any circumstances in which such offer or solicitation is unlawful. Neither the delivery of this prospectus supplement and the accompanying prospectus nor any sale made hereunder or thereunder shall, under any circumstances, create any implication that there has been no change in our affairs since the date hereof or that the information contained herein or therein is correct as of any time subsequent to the date hereof.

Issuer		McKesson Corporation
Securities Offered		$               aggregate principal amount of notes, consisting of:
		• $               aggregate principal amount of                     % Notes due 2013.
		• $               aggregate principal amount of                     % Notes due 2017.
Maturity		2013 notes —                     , 2013.
		2017 notes —                     , 2017.
Interest Rate		2013 notes —      % per year.
		2017 notes —      % per year.
Interest Payment Dates		Interest will be paid on                     and                     of each year, beginning on                     , 2007. Interest on the notes will accrue from                     , 2007.
Use of Proceeds		We estimate that we will receive approximately $                     million from the sale of the notes, after deducting underwriting discounts and estimated offering expenses. We will use the net proceeds from this offering to repay borrowings outstanding under our interim credit facility.
Optional Redemption		Upon 30 days’ notice to noteholders, we may redeem the notes of each series for cash in whole, at any time, or in part, from time to time, prior to maturity, at redemption prices that include accrued and unpaid interest and a make-whole premium. See “Description of Notes — Optional Redemption”.
Change of Control		Upon the occurrence of both (1) a change of control of us and (2) a downgrade of the notes below an investment grade rating by each of Fitch Ratings, Moody’s Investors Service, Inc. and Standard & Poor’s Ratings Services within a specified period, we will be required to make an offer to purchase the notes of each series at a price equal to 101% of the principal amount of such series, plus accrued and unpaid interest to the date of repurchase. See “Description of Notes — Change of Control”.
Other Covenants		We will issue the notes under an indenture with The Bank of New York Trust Company, N.A., as trustee. The indenture includes certain covenants, including limitations on:
		• liens;
		• sale and lease-backs; and
		• mergers or consolidations with another entity.
		These covenants are subject to a number of important exceptions, limitations and qualifications that are described under “Description of Notes — Certain Covenants”.
Ranking		Each series of notes will be unsecured and will rank equally with all our existing and future unsecured and unsubordinated indebtedness from time to time outstanding.
		The indenture does not limit the amount of debt we may incur.
Further Issues		We may create and issue further notes of each series ranking equally and ratably with the notes of such series in all respects, so that such further notes shall be consolidated and form a single series with the notes of such series.

USE OF PROCEEDS

      We estimate that the net proceeds from this offering will be approximately $                     million, after deducting underwriting discounts and estimated offering expenses. We plan to use the net proceeds from the sale of the notes to repay borrowings outstanding under the interim credit facility that we entered into to fund a portion of the merger consideration for the recent acquisition of Per-Se Technologies, Inc. The interim credit facility matures on January 25, 2008, and bears interest at a floating rate based on either a Eurodollar rate or a base rate. At January 31, 2007, there was approximately $1.0 billion outstanding under the interim credit facility. As of such date, our borrowings under the interim credit facility accrued interest at the rate of 5.82% per year. We intend to use any remaining net proceeds for general corporate purposes.

      Certain affiliates of each of the underwriters are lenders and/or agents under our interim credit facility and our revolving credit facility. Therefore, affiliates of the underwriters will receive their pro rata share of the net proceeds from this offering used to refinance the interim credit facility.

CAPITALIZATION

      The following table sets forth our short-term debt and total capitalization as of December 31, 2006:

      You should read this table in conjunction with Management’s Discussion and Analysis of Financial Condition and Results of Operations and our historical financial statements and notes to those financial statements that are incorporated by reference in this prospectus supplement and the accompanying prospectus.

SELECTED CONSOLIDATED FINANCIAL INFORMATION

      We have derived the following results of operations and balance sheet data for and as of the end of fiscal years 2002, 2003, 2004, 2005 and 2006 from our audited consolidated financial statements. The selected financial data for the nine months ended December 31, 2005 and 2006 have been derived from our unaudited consolidated financial statements. The unaudited financial information, in the opinion of management, contains all adjustments necessary for a fair presentation of the information for the periods presented. The results for the nine months ended December 31, 2006 may not be indicative of the results to be achieved for the entire fiscal year. You should read the information set forth below in conjunction with our consolidated financial statements and related notes and other financial information incorporated by reference into this prospectus supplement and the accompanying prospectus. See “Where You Can Find More Information” in this prospectus supplement.

DESCRIPTION OF NOTES

      This description of the notes supplements and, to the extent it is inconsistent, replaces, the description of the general provisions of the notes and the indenture in the accompanying prospectus. The notes are “Senior Debt Securities,” as that term is used in the accompanying prospectus.

General

      The notes will be issued under an indenture, dated as of                     , 2007, between us and The Bank of New York Trust Company, N.A. You may request a copy of the indenture and the form of notes from the trustee.

      We will issue the notes of each series in fully registered book-entry form without coupons and in denominations of $1,000 and integral multiples of $1,000 thereafter. We do not intend to apply for the listing of the notes of either series on a national securities exchange or for quotation of such notes on any automated dealer quotation system.

      The following statement relating to the notes and the indenture are summaries of certain provisions thereof and are subject to the detailed provisions of the indenture, to which reference is hereby made for a complete statement of such provisions. Certain provisions of the indenture are summarized in the accompanying prospectus. We encourage you to read the summaries of the notes and the indenture in both this prospectus supplement and the accompanying prospectus, as well as the form of notes and the indenture.

      The notes will be our unsecured senior obligations. The cover page of this prospectus supplement sets forth the maturity dates, the aggregate principal amounts and the interest rates of the notes. The notes will bear interest from the date of issuance, payable semiannually on each                     and                     , commencing                     , 2007, to the persons in whose names the notes are registered at the close of business on the immediately preceding each                     or the                     immediately preceding each                     . Interest will be computed on the basis of a 360-day year composed of twelve 30-day months. Payments of principal and interest to owners of book-entry interests (as described below) are expected to be made in accordance with the procedures of The Depository Trust Company (“DTC”) and its participants in effect from time to time.

      We may, without the consent of the holders of the notes, create and issue additional notes ranking equally with either series of notes in all respects, except for the issue price and the date from which interest accrues. No additional notes may be issued if an event of default has occurred and is continuing with respect to such series of notes.

Optional Redemption

      The notes of each series will be redeemable, in whole at any time or in part from time to time, at our option at a redemption price equal to the greater of:

plus, in each case, accrued interest thereon to the date of redemption. Notwithstanding the foregoing, installments of interest on notes that are due and payable on interest payment dates falling on or prior to a redemption date will be payable on the interest payment date to the registered holders as of the close of business on the relevant record date according to the notes and the indenture.

      “Comparable Treasury Issue” means the United States Treasury security selected by the Quotation Agent as having a maturity comparable to the remaining term of the notes of the applicable series to be redeemed

that would be utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities of comparable maturity to the remaining term of such series of notes.

      “Comparable Treasury Price” means, with respect to any redemption date, (i) the average of four Reference Treasury Dealer Quotations for such redemption date, after excluding the highest and lowest such Reference Treasury Dealer Quotations, or (ii) if the trustee obtains fewer than four such Reference Treasury Dealer Quotations, the average of all such quotations.

      “Quotation Agent” means the Reference Treasury Dealer appointed by us.

      “Reference Treasury Dealer” means (i) Banc of America Securities LLC (or its affiliates that are Primary Treasury Dealers) and its successors; provided, however, that if any of the foregoing shall cease to be a primary U.S. Government securities dealer in New York City (a “Primary Treasury Dealer”), we will substitute therefor another Primary Treasury Dealer, and (ii) any other Primary Treasury Dealer selected by us.

      “Reference Treasury Dealer Quotations” means, with respect to each Reference Treasury Dealer and any redemption date, the average, as determined by the trustee, of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing to the trustee by such Reference Treasury Dealer at 5:00 p.m., New York City time, on the third business day preceding such redemption date.

      “Treasury Rate” means, with respect to any redemption date, the rate per annum equal to the semiannual equivalent yield to maturity of the Comparable Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal to the Comparable Treasury Price of such redemption date.

      Notice of any redemption will be mailed at least 30 days but not more than 60 days before the redemption date to each registered holder of the series of notes to be redeemed. Unless we default in payment of the redemption price, on and after the redemption date, interest will cease to accrue on the notes of such series or portions thereof called for redemption. If less than all of the notes of a series are to be redeemed, the notes of such series to be redeemed will be selected by the trustee by a method the trustee deems to be fair and appropriate.

Change of Control

      If a Change of Control Triggering Event occurs, unless we have exercised our right to redeem the notes as described above, holders of notes will have the right to require us to repurchase all or any part (equal to $1,000 or an integral multiple of $1,000 in excess thereof) of their notes pursuant to the offer described below (the “Change of Control Offer”) on the terms set forth in the notes. In the Change of Control Offer, we will be required to offer payment in cash equal to 101% of the aggregate principal amount of notes repurchased plus accrued and unpaid interest, if any, on the notes repurchased, to the date of purchase (the “Change of Control Payment”). Within 30 days following any Change of Control Triggering Event, we will be required to mail a notice to holders of notes describing the transaction or transactions that constitute the Change of Control Triggering Event and offering to repurchase the notes on the date specified in the notice, which date will be no earlier than 30 days and no later than 60 days from the date such notice is mailed (the “Change of Control Payment Date”), pursuant to the procedures required by the notes and described in such notice. We must comply with the requirements of Rule 14e-1 under the Exchange and any other securities laws and regulations thereunder to the extent those laws and regulations are applicable in connection with the repurchase of the notes as a result of a Change of Control Triggering Event. To the extent that the provisions of any securities laws or regulations conflict with the Change of Control provisions of the notes, we will be required to comply with the applicable securities laws and regulations and will not be deemed to have breached our obligations under the Change of Control provisions of the notes by virtue of such conflicts.

      On the Change of Control Payment Date, we will be required, to the extent lawful, to:

      The definition of Change of Control includes a phrase relating to the direct or indirect sale, lease, transfer, conveyance or other disposition of “all or substantially all” of the properties or assets of McKesson and its subsidiaries taken as a whole. Although there is a limited body of case law interpreting the phrase “substantially all,” there is no precise established definition of the phrase under applicable law. Accordingly, the ability of a holder of notes to require McKesson to repurchase its notes as a result of a sale, lease, transfer, conveyance or other disposition of less than all of the assets of McKesson and its subsidiaries taken as a whole to another Person (as defined in the indenture) or group may be uncertain.

      For purposes of the foregoing discussion of a repurchase at the option of holders, the following definitions are applicable:

      “Below Investment Grade Rating Event” means the notes are rated below an Investment Grade Rating by each of the Rating Agencies (as defined below) on any date from the date of the public notice of an arrangement that could result in a Change of Control until the end of the 60-day period following public notice of the occurrence of the Change of Control (which 60-day period shall be extended so long as the rating of the notes is under publicly announced consideration for possible downgrade by any of the Rating Agencies).

      “Change of Control” means the occurrence of any of the following: (1) the direct or indirect sale, transfer, conveyance or other disposition (other than by way of merger or consolidation), in one or a series of related transactions, of all or substantially all of the properties or assets of McKesson and its subsidiaries taken as a whole to any Person other than McKesson or one of its subsidiaries; (2) the consummation of any transaction (including, without limitation, any merger or consolidation) the result of which is that any Person becomes the beneficial owner, directly or indirectly, of more than 50% of the then outstanding number of shares of McKesson’s voting stock; or (3) the first day on which a majority of the members of McKesson’s Board of Directors are not Continuing Directors. Notwithstanding the foregoing, a transaction will not be deemed to involve a change of control if (i) we become a wholly owned subsidiary of a holding company and (ii) the holders of the voting stock of such holding company immediately following that transaction are substantially the same as the holders of our voting stock immediately prior to that transaction.

      “Change of Control Triggering Event” means the occurrence of both a Change of Control and a Below Investment Grade Rating Event.

      “Continuing Directors” means, as of any date of determination, any member of the Board of Directors of McKesson who (1) was a member of such Board of Directors on the date of the issuance of the notes; or (2) was nominated for election or elected to such Board of Directors with the approval of a majority of the Continuing Directors who were members of such Board of Directors at the time of such nomination or election (either by a specific vote or by approval of McKesson’s proxy statement in which such member was named as a nominee for election as a director, without objection to such nomination).

      “Fitch” means Fitch Ratings.

      “Investment Grade Rating” means a rating equal to or higher than BBB- (or the equivalent) by Fitch, Baa3 (or the equivalent) by Moody’s and BBB-(or the equivalent) by S&P.

      “Moody’s” means Moody’s Investors Service, Inc.

      “Rating Agencies” means (1) each of Fitch, Moody’s and S&P; and (2) if any of Fitch, Moody’s or S&P ceases to rate the notes or fails to make a rating of the notes publicly available for reasons outside of our control, a “nationally recognized statistical rating organization” within the meaning of Rule 15c3-1(c)(2)(vi)(F) under the Exchange Act, selected by us (as certified by a resolution of our Board of Directors) as a replacement agency for Fitch, Moody’s or S&P, or all of them, as the case may be.

      “S&P” means Standard & Poor’s Ratings Services, a division of The McGraw-Hill Companies, Inc.

Certain Covenants

Definitions

      The term “Attributable Debt” shall mean in connection with a sale and lease-back transaction the lesser of (a) the fair value of the assets subject to such transaction, as determined by McKesson’s Board of Directors, or (b) the present value of the obligations of the lessee for net rental payments during the term of any lease discounted at the rate of interest set forth or implicit in the terms of such lease or, if not practicable to determine such rate, the weighted average interest rate per annum borne by the debt securities of each series outstanding pursuant to the indenture and subject to limitations on sale and lease-back transaction covenants, compounded semi-annually in either case as determined by our principal accounting or financial officer.

      The term “Consolidated Subsidiary” shall mean any Subsidiary substantially all the property of which is located, and substantially all the operations of which are conducted, in the United States of America whose financial statements are consolidated with our financial statements in accordance with generally accepted accounting principles.

      The term “Exempted Debt” shall mean the sum of the following as of the date of determination: (1) Indebtedness of ours and our Consolidated Subsidiaries incurred after the date of issuance of the Notes and secured by liens not permitted by the limitation on liens provisions, and (2) Attributable Debt of ours and our Consolidated Subsidiaries in respect of every sale and lease-back transaction entered into after the date of the issuance of the Notes, other than leases permitted by the limitation on sale and lease-back provisions.

      The term “Indebtedness” shall mean all items classified as indebtedness on our most recently available consolidated balance sheet, in accordance with generally accepted accounting principles.

      The term “Subsidiary” shall mean any corporation of which at least a majority of the outstanding stock having voting power under ordinary circumstances for the election of the board of directors of said corporation shall at the time be owned by us or by us and one or more Subsidiaries or by one or more Subsidiaries.

Limitation on Liens

      We covenant that, so long as any of the notes remain outstanding, we will not, and will not permit any Consolidated Subsidiary, to create or assume any Indebtedness for money borrowed which is secured by a lien (as defined in the indenture) upon any assets, whether now owned or hereafter acquired, of ours or any such Consolidated Subsidiary without equally and ratably securing the notes by a lien ranking ratably with and equally to such secured Indebtedness, except that the foregoing restriction shall not apply to:

      Notwithstanding the above, we or any of our Consolidated Subsidiaries may, without securing the notes, create or assume any Indebtedness which is secured by a lien which would otherwise be subject to the foregoing restrictions, provided that after giving effect thereto the Exempted Debt then outstanding at such time does not exceed 10% of our total assets on a consolidated basis.

Limitation on Sale and Lease-Back Transactions

      Sale and lease-back transactions, except such transactions involving leases for less than three years, by us or any Consolidated Subsidiary of any assets are prohibited unless (a) we or such Consolidated Subsidiary would be entitled to incur Indebtedness secured by a lien on the assets to be leased in an amount at least equal to the Attributable Debt in respect of such transaction without equally and ratably securing the notes, or (b) the proceeds of the sale of the assets to be leased are at least equal to their fair market value and the proceeds are applied to the purchase or acquisition, or, in the case of real property, the construction, of assets or to the retirement of Indebtedness. The foregoing limitation will not apply, if at the time we or any Consolidated Subsidiary enters into such sale and lease-back transaction, and after giving effect thereto, Exempted Debt does not exceed 10% of our total assets on a consolidated basis.

Consolidation, Merger or Sale

      We cannot consolidate or merge with or into, or transfer or lease all or substantially all of our assets to, any person unless (a) we will be the continuing corporation or (b) the successor corporation or person to which our assets are transferred or leased is a corporation organized under the laws of the United States, any state of the United States or the District of Columbia and it expressly assumes our obligations on the notes and under the indenture. In addition, we cannot effect such a transaction unless immediately after giving effect to such transaction, no default or event of default under the indenture shall have occurred and be continuing. Subject to certain exceptions, when the person to whom our assets are transferred or leased has assumed our obligations under the notes and the indenture, we shall be discharged from all our obligations under the notes and the indenture, except in limited circumstances.

      This covenant would not apply to any recapitalization transaction, a change of control of McKesson or a highly leveraged transaction, unless the transaction or change of control were structured to include a merger or consolidation or transfer or lease of all or substantially all of our assets.

Book-Entry System

      The certificates representing the notes of each series will be issued in the form of one or more fully registered global notes without coupons (the “Global Note”) and will be deposited with, or on behalf of, DTC and registered in the name of Cede & Co., as the nominee of DTC. Except in limited circumstances, the notes will not be issuable in definitive form. Unless and until they are exchanged in whole or in part for the individual notes represented thereby, any interests in the Global Note may not be transferred except as a whole by DTC to a nominee of DTC or by a nominee of DTC to DTC or another nominee of DTC or by DTC or any nominee of DTC to a successor depository or any nominee of such successor. See “Description of Debt Securities — Registered Global Securities” in the accompanying prospectus.

      DTC has advised us that DTC is a limited-purpose trust company organized under the New York Banking Law, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act. DTC holds securities that its participants (“Direct Participants”) deposit with DTC. DTC also facilitates the post-trade settlement among Direct Participants of sales and other securities transactions in deposited securities through electronic computerized book-entry transfers and pledges between Direct Participants’ accounts, thereby eliminating the need for physical movement of securities certificates. Direct Participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations, and certain other organizations. DTC is a wholly-owned subsidiary of The Depository Trust & Clearing Corporation (“DTCC”). DTCC, in turn, is owned by a number of Direct Participants of DTC and Members of the National Securities Clearing Corporation, Fixed Income Clearing Corporation and Emerging Markets Clearing Corporation (NSCC, FICC, and EMCC, also subsidiaries of DTCC), as well as by The New York Stock Exchange, Inc., the American Stock Exchange LLC and the National Association of Securities Dealers, Inc. Access to the DTC system is also available to others such as both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, and clearing corporations that clear through or maintain a custodial relationship with a Direct Participant, either directly or indirectly. The rules applicable to DTC and its Participants are on file with the SEC.

      The information in this section concerning DTC and DTC’s book-entry system has been obtained from sources that we believe to be reliable, but we take no responsibility for the accuracy thereof.

Same-Day Funds Settlement and Payment

      Settlement for the notes will be made by the underwriters in immediately available funds. All payments of principal and interest in respect of notes in book-entry form will he made by us in immediately available funds to the accounts specified by DTC.

      Secondary trading in long-term notes and debentures of corporate issuers is generally settled in clearing houses or next-day funds. In contrast, the notes will trade in DTC’s Same-Day Funds Settlement System until maturity or until the notes are issued in certificated form, and secondary market trading activity in the notes will therefore be required by DTC to settle in immediately available funds. No assurance can be given as to the effect, if any, of settlement in immediately available funds on trading activity in the notes.

Concerning the Trustee

      The Bank of New York Trust Company, N.A. will be the trustee under the indenture. We may maintain deposit accounts or conduct other banking transactions with the trustee in the ordinary course of business.

UNDERWRITING

      Subject to the terms and conditions contained in an underwriting agreement, we have agreed to sell to the underwriters, for whom Banc of America Securities LLC and Wachovia Capital Markets, LLC are acting as representatives, and these underwriters severally have agreed to purchase from us, the principal amount of the notes listed opposite their names below:

      The underwriters have agreed to purchase all of the notes of a series sold pursuant to the underwriting agreement if any of such notes are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the non-defaulting underwriters may be increased or the underwriting agreement may be terminated.

      We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make in respect of those liabilities.

      The underwriters are offering the notes, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel, including the validity of the notes, and other conditions contained in the underwriting agreement, such as the receipt by the underwriters of officer’s certificates and legal opinions. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Commissions and Discounts

      The underwriters have advised us that they propose initially to offer the notes to the public at the public offering prices on the cover page of this prospectus supplement, and to dealers at these prices less concessions not in excess of      % of the principal amount of the 2013 notes and      % of the principal amount of the 2017 notes. The underwriters may allow, and the dealers may reallow, discounts not in excess of      % of the principal amount of the 2013 notes and      % of the principal amount of the 2017 notes to other dealers. After the initial public offering, the public offering prices, concessions and discounts may be changed.

      The following table summarizes the compensation to be paid by us to the underwriters.

      The expenses of the offering, not including the underwriting discount, are estimated to be $          and are payable by us.

New Issue of Notes

      The notes are new issues of securities with no established trading market. We do not intend to apply for listing of either series of notes on any national securities exchange or for quotation of the notes on any automated dealer quotation system. We have been advised by the underwriters that they presently intend to

make a market in each series of notes after completion of the offering. However, they are under no obligation to do so and may discontinue any market-making activities at any time without any notice. We cannot assure the liquidity of the trading markets for the notes or that active public markets for the notes will develop. If active public trading markets for the notes do not develop, the market prices and liquidity of the notes may be adversely affected.

Price Stabilization and Short Positions

      In connection with the offering, the underwriters are permitted to engage in transactions that stabilize the market prices of the notes. Such transactions consist of bids or purchases to peg, fix or maintain the prices of the notes. If the underwriters create a short position in the notes in connection with the offering, i.e., if they sell more notes of that series than are on the cover page of this prospectus supplement, the underwriters may reduce that short position by purchasing notes of that series in the open market. Purchases of a security to stabilize the price or to reduce a short position could cause the price of the security to be higher than it might be in the absence of such purchases.

      Neither we nor any of the underwriters makes any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the prices of the notes. In addition, neither we nor any of the underwriters makes any representation that the underwriters will engage in these transactions or that these transactions, once commenced, will not be discontinued without notice.

Other Relationships

      Some of the underwriters and their affiliates have engaged in, and may in the future engage in, investment banking, commercial banking and other commercial dealings with us in the ordinary course of business. In particular, the affiliates of some of the underwriters are participants in our revolving credit facility described in our filings with the SEC. They have received customary fees, commissions or other payments for these transactions. In addition, as described under “Use of Proceeds,” we intend to use all of the net proceeds from this offering to repay our interim credit facility under which affiliates of Banc of America Securities LLC and Wachovia Capital Markets, LLC serve as agents. Because the underwriters or their affiliated or associated persons will receive more than 10% of the proceeds of the offering as repayment for such debt, the offering is made in compliance with the applicable provisions of Section 2710(h)(1) and Rule 2720 of the NASD Conduct Rules.

LEGAL MATTERS

      The legality of the notes offered hereby will be passed upon for us by Skadden, Arps, Slate, Meagher & Flom LLP, Los Angeles, California, and for the underwriters by Mayer, Brown, Rowe & Maw LLP, Chicago, Illinois.

EXPERTS

      The consolidated financial statements, the related consolidated financial statement schedules, and management’s report on the effectiveness of internal control over financial reporting incorporated in this prospectus supplement by reference from McKesson’s Annual Report on Form 10-K for the fiscal year ended March 31, 2006, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report, which are incorporated herein by reference, and have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

      The SEC allows us to “incorporate by reference” into this prospectus supplement the information we file with the SEC, which means:

      We incorporate by reference the documents listed below and any future documents we file with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, until we terminate this offering:

      You can obtain any of the filings incorporated by reference in this document through us, or from the SEC through the SEC’s web site http://www.sec.gov or at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, DC 20549. You may obtain information on the operation of the SEC’s Public Reference Room by calling 1-800-SEC-0330. Documents incorporated by reference are available from us without charge, excluding any exhibits to those documents unless the exhibit is specifically incorporated by reference as an exhibit in this prospectus supplement. You can obtain documents incorporated by reference in this prospectus supplement by requesting them in writing or by telephone from us at the following address:

McKesson Corporation

One Post Street

San Francisco, California 94104

Attn: Corporate Secretary

Telephone: (415) 983-8300

      Any statement contained in a document incorporated by reference herein shall be deemed to be modified or superseded for purposes of the prospectus supplement to the extent that a statement contained herein or in any other subsequently filed document that is incorporated by reference herein modifies or supersedes such earlier statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of the prospectus supplement.

PROSPECTUS

$1,500,000,000

McKesson Corporation

Common Stock

Preferred Stock

Depositary Shares

Debt Securities

Warrants

Stock Purchase Contracts

Stock Purchase Units

McKESSON CORPORATION

         The common stock of McKesson Corporation is listed on the New York Stock Exchange under the symbol “MCK.” Our principal executive offices are located at McKesson Plaza, One Post Street, San Francisco, California 94104, and our telephone number is (415) 983-8300.

         We urge you to read carefully this prospectus and the accompanying prospectus supplement, which will describe the specific terms of the securities being offered to you, before you make your investment decision.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus or the accompanying prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

This prospectus may not be used to sell securities unless accompanied by a prospectus supplement.

The date of this prospectus is August 4, 2005.

TABLE OF CONTENTS

         Unless otherwise indicated or the context otherwise requires, all references in this prospectus to “McKesson,” “the company,” “we,” “our,” “us” or similar terms refer to McKesson Corporation, together with its subsidiaries.

ABOUT THIS PROSPECTUS

         This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission (the “Commission” or “SEC”), using a “shelf” registration process. Under this shelf process, we may sell any combination of the securities described in this prospectus in one or more offerings up to a total dollar amount of $1,500,000,000. This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. You should read both this prospectus and any prospectus supplement together with additional information described under the heading “Where You Can Find More Information.”

WHERE YOU CAN FIND MORE INFORMATION

         We file reports, proxy statements, and other information with the SEC. Such reports, proxy statements, and other information concerning us can be read and copied at the SEC’s Public Reference Room at 450 Fifth Street, N.W., Room 1024, Washington, D.C. 20549 or on the Internet at http://www.sec.gov. Please call the SEC at 1-800-SEC-0330 for further information on the Public Reference Room. Our common stock is listed on the New York Stock Exchange, and these reports, proxy statements and other information are also available for inspection at the offices of the New York Stock Exchange, 20 Broad Street, New York, New York 10005.

         This prospectus is part of a registration statement filed with the SEC by us. The full registration statement can be obtained from the SEC as indicated above, or from us.

         The SEC allows us to “incorporate by reference” the information we file with the SEC. This permits us to disclose important information to you by referring to these filed documents. Any information referred to in this way is considered part of this prospectus, and any information filed with the SEC by us after the date of this prospectus will automatically be deemed to update and supersede this information. We incorporate by reference the following documents that have been filed with the SEC (other than information in such documents that is not deemed to be filed):

         We also incorporate by reference any future filings (other than information in such documents that is not deemed to be filed) made with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) until we file a post-effective amendment which indicates the termination of the offering of the securities made by this prospectus.

         We will provide without charge upon written or oral request a copy of any or all of the documents that are incorporated by reference into this prospectus, other than exhibits which are specifically incorporated by reference into such documents. Requests should be directed to our Corporate Secretary at McKesson Corporation, McKesson Plaza, One Post Street, San Francisco, California 94104. Our telephone number is (415) 983-8300.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

         This prospectus and the documents incorporated by reference herein include forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”) and Section 21E of the Exchange Act. Some of the forward-looking statements can be identified by the use of forward-looking words including, but not limited to, “believes,” “expects,” “anticipates,” “may,” “will,” “should,” “seeks,” “approximately,” “intends,” “plans,” or “estimates” or the negative of those words or other comparable terminology. Forward-looking statements involve risks and uncertainties that could cause actual results to differ materially from those in the forward-looking statements. These factors include, but are not limited to, those discussed under “Additional Factors That May Affect Future Results” in our Annual Report on Form 10-K, in any prospectus supplement related hereto, and in other information contained in our publicly available SEC filings and press releases.

         You should not place undue reliance on any such forward-looking statements, which speak only as of the date hereof. Except to the extent required by federal securities laws, we do not intend to update forward-looking information or to release the results of any future revisions we may make to forward-looking statements to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events.

McKESSON CORPORATION

         We are a Fortune 15 corporation providing supply, information and care management products and services designed to reduce costs and improve quality across the healthcare industry. We conduct our business through three segments: Pharmaceutical Solutions, Medical-Surgical Solutions and Provider Technologies.

         Our principal executive offices are located at McKesson Plaza, One Post Street, San Francisco, California 94104, and our telephone number is (415) 983-8300.

USE OF PROCEEDS

         Unless otherwise set forth in a prospectus supplement with respect to the proceeds from the sale of the particular securities to which such prospectus supplement relates, we intend to use the net proceeds from the sale of the offered securities for general corporate purposes, including repayment or redemption of outstanding debt or preferred stock, the possible acquisition of related businesses or assets thereof, and working capital needs.

DESCRIPTION OF SECURITIES

         This prospectus contains a summary of our common stock, preferred stock, depositary shares, debt securities, warrants, stock purchase contracts and stock purchase units. These summaries are not meant to be a complete description of each security. The particular terms of any security to be issued pursuant hereto will be set forth in a related prospectus supplement. This prospectus and the accompanying prospectus supplement will contain the material terms and conditions for each security.

DESCRIPTION OF CAPITAL STOCK

         The following descriptions of our capital stock and of certain provisions of Delaware law do not purport to be complete and are subject to and qualified in their entirety by reference to our restated certificate of incorporation and bylaws and the Delaware General Corporation Law (“DGCL”), and, with respect to certain rights of holders of shares of common stock, our rights agreement. Copies of such documents have been filed with the SEC and are filed as exhibits to the registration statement to which this prospectus is a part.

         As of the date hereof, our authorized capital stock consists of 900,000,000 shares, of which 800,000,000 shares are common stock, par value $0.01 per share, and 100,000,000 shares are preferred stock, par value $0.01 per share. As of April 30, 2005, there were 299,979,779 shares of common stock issued and outstanding, and no shares of preferred stock issued and outstanding. Of the preferred stock, 10,000,000 shares have been designated Series A Junior Participating Preferred Stock and reserved for issuance pursuant to our rights agreement. All of our outstanding shares of common stock are fully paid and non-assessable.

         Our common stock is listed on the New York Stock Exchange and the Pacific Exchange under the symbol “MCK.”

         In February 1997, McKesson Financing Trust issued an aggregate of 4,123,720 5% Trust Convertible Preferred Securities. Each trust security is convertible into common stock at any time prior to the close of business on the business day prior to June 1, 2027 (or prior to the date of redemption of the trust security), at the option of the holder, at the rate of 1.3418 shares of common stock for each trust security (equivalent to a conversion price of $37.26 per share of common stock), subject to adjustment in certain circumstances. As described in our Annual Report on Form 10-K for the fiscal year ended March 31, 2005, we do not consolidate our investment in McKesson Financing Trust.

Common Stock

         Dividends Rights. Subject to the dividend rights of the holders of any outstanding series of preferred stock, the holders of shares of common stock are entitled to receive ratably dividends out of assets legally available therefor at such times and in such amounts as our board of directors may from time to time determine.

         Rights Upon Liquidation. Upon liquidation, dissolution or winding up of our affairs, the holders of common stock are entitled to share ratably in our assets that are legally available for distribution, after payment of all debts, other liabilities and any liquidation preferences of outstanding preferred stock.

         Conversion, Redemption and Preemptive Rights. Holders of our common stock have no conversion, redemption, preemptive or similar rights.

         Voting Rights. Each outstanding share of common stock is entitled to one vote on all matters submitted to a vote of stockholders. Our restated certificate of incorporation does not provide for cumulative voting in the election of directors.

Preferred Stock

         Our restated certificate of incorporation authorizes our board of directors, without further stockholder action, to provide for the issuance of up to 100,000,000 shares of preferred stock, in one or more series, and to fix the designations, terms, and relative rights and preferences, including the dividend rate, voting rights, conversion rights, redemption and sinking fund provisions and liquidation values of each of these series. We may amend from time to time our restated certificate of incorporation to increase the number of authorized shares of preferred stock. Any such amendment would require the approval of the holders of a majority of our stock entitled to vote.

         The particular terms of any series of preferred stock that we offer under this prospectus will be described in the applicable prospectus supplement relating to that series of preferred stock. Those terms may include:

         If the terms of any series of preferred stock being offered differ from the terms set forth in this prospectus, those terms will also be disclosed in the applicable prospectus supplement relating to that series of preferred stock. The summary in this prospectus is not complete. You should refer to the certificate of designations establishing a particular series of preferred stock which will be filed with the Secretary of State of the State of Delaware and the SEC in connection with the offering of the preferred stock.

         Each prospectus supplement may describe certain U.S. federal income tax considerations applicable to the purchase, holding and disposition of the preferred stock that prospectus supplement covers.

         Dividend Rights. The preferred stock will be preferred over the common stock as to payment of dividends. Before any dividends or distributions (other than dividends or distributions payable in common stock or other stock ranking junior to that series of preferred stock as to dividends and upon liquidation) on the common stock or other stock ranking junior to that series of preferred stock as to dividends and upon liquidation shall be declared and set apart for payment or paid, the holders of shares of each series of preferred stock (unless otherwise set forth in the applicable prospectus supplement) will be entitled to receive dividends when, as and if declared by our board of directors or, if dividends are cumulative, full cumulative dividends for the current and all prior dividend periods. We will pay those dividends either in cash, shares of preferred stock, or otherwise, at the rate and on the date or dates set forth in the applicable prospectus supplement. With respect to each series of preferred stock that has cumulative dividends, the dividends on each share of the series will be cumulative from the date of issue of the share unless some other date is set forth in the prospectus supplement relating to the series. Accruals of dividends will not bear interest. The applicable prospectus supplement will indicate the relative ranking of the particular series of the preferred stock as to the payment of dividends, as compared with then-existing and future series of preferred stock.

         Rights Upon Liquidation. The preferred stock of each series will be preferred over the common stock and other stock ranking junior to that series of preferred stock as to assets, so that the holders of that series of

preferred stock (unless otherwise set forth in the applicable prospectus supplement) will be entitled to be paid, upon our voluntary or involuntary liquidation, dissolution or winding up, and before any distribution is made to the holders of common stock and other stock ranking junior to that series of preferred stock, the amount set forth in the applicable prospectus supplement. However, in this case the holders of preferred stock of that series will not be entitled to any other or further payment. If upon any liquidation, dissolution or winding up, our net assets are insufficient to permit the payment in full of the respective amounts to which the holders of all outstanding preferred stock are entitled, our entire remaining net assets will be distributed among the holders of each series of preferred stock in amounts proportional to the full amounts to which the holders of each series are entitled, subject to any provisions of any series of preferred stock that rank it junior or senior to other series of preferred stock upon liquidation. The applicable prospectus supplement will indicate the relative ranking of the particular series of the preferred stock upon liquidation, as compared with then-existing and future series of preferred stock.

         Conversion, Redemption or Exchange Rights. The shares of a series of preferred stock will be convertible at the option of the holder of the preferred stock, redeemable at our option or the holder, as applicable, or exchangeable at our option, into another security, in each case, to the extent set forth in the applicable prospectus supplement.

         Voting Rights. Except as indicated in the applicable prospectus supplement or as otherwise from time to time required by law, the holders of preferred stock will have no voting rights.

Anti-Takeover Effects of Provisions of the Our Restated Certificate of Incorporation and Bylaws

         Our restated certificate of incorporation and bylaws contain certain provisions that may be deemed to have an anti-takeover effect and may delay, deter or prevent a tender offer or takeover attempt that a stockholder might consider in its best interest, including those attempts that might result in a premium over the market price for the shares held by stockholders.

         Pursuant to our restated certificate of incorporation, our board of directors is divided into three classes serving staggered three-year terms. Directors can be removed from office only for cause and only by the affirmative vote of the holders of at least a majority of the voting power of the then outstanding shares of any class or series of our capital stock entitled to vote generally in the election of directors. Vacancies and newly created directorships on our board of directors may be filled only by a majority of the remaining directors or by the plurality vote of the stockholders.

         Our restated certificate of incorporation also provides that any action required or permitted to be taken by the holders of common stock may be effected only at an annual or special meeting of such holders, and that stockholders may act in lieu of such meetings only by unanimous written consent. Our bylaws provide that special meetings of holders of common stock may be called only by our Chairman or President or board of directors. Holders of common stock are not permitted to call a special meeting or to require that our board of directors call a special meeting of stockholders.

         Our bylaws establish an advance notice procedure for the nomination, other than by or at the direction of our board of directors, of candidates for election as directors as well as for other stockholder proposals to be considered at annual meetings of stockholders. In general, notice of intent to nominate a director or raise business at such meetings must be received by us not less than 90 nor more than 120 days prior to the date of the annual meeting and must contain certain specified information concerning the person to be nominated or the matters to be brought before the meeting and concerning the stockholder submitting the proposal.

         Our restated certificate of incorporation provides that certain provisions of the bylaws may only be amended by the affirmative vote of the holders of 75% of our outstanding shares entitled to vote. Our restated certificate of incorporation also provides that, in addition to any affirmative vote required by law, the affirmative vote of holders of 80% of our outstanding voting stock and two-thirds of the voting stock other than voting stock held by an interested stockholder shall be necessary to approve certain business combinations proposed by an interested stockholder.

         The foregoing summary is qualified in its entirety by the provisions of our restated certificate of incorporation and bylaws, copies of which have been filed with the SEC.

Rights Plan

         Pursuant to a rights agreement, our board of directors declared a dividend distribution of one right for each outstanding share of common stock to stockholders of record at October 22, 2004. Each right entitles the registered holder to purchase from us a unit consisting of one one-hundredth of a share of Series A Junior Participating Preferred Stock at a purchase price of $100 per unit. The rights expire on October 22, 2014, unless redeemed earlier by our board of directors. The terms of the rights are set forth in a rights agreement between us and a rights agent, a copy of which is filed with the SEC. The following summary outlines certain provisions of the rights agreement and is qualified in its entirety by reference to our rights agreement.

         The rights are attached to all common stock certificates representing shares outstanding at the record date and shares issued between the record date and the distribution date, and no separate rights certificates have been distributed. The rights will separate from the common stock, separate rights certificates will be issued (which will then be the sole evidence of the rights) and a distribution date will occur upon the earlier to occur of:

         (1)            ten business days following the date of a public announcement by us or an acquiring person that there is such an acquiring person (such date is referred to as the “stock acquisition date”),

         (2)            ten business days (or such later date as our board of directors may determine) following commencement of a tender or exchange offer that would result in the offeror beneficially owning 15% or more of the common stock, or

         (3)            ten business days after our of directors determine that the ownership of 10% or more of our outstanding common stock by a person is (A) intended to cause us to repurchase the common stock beneficially owned by such person or to cause pressure on us to take action or enter into a transaction or series of transactions intended to provide such person with short-term financial gain under circumstances where our directors determine that the best long-term interest of the company and its stockholders would not be served by taking such action or entering into such transactions or series of transactions at that time, or (B) is causing, or is reasonably likely to cause, a material adverse impact on us.

         The term “acquiring person” means any person who, together with affiliates and associates, acquires beneficial ownership of shares of our common stock representing 15% or more of our outstanding common stock, but shall not include us, any of our subsidiaries, any of our employee benefit plans, any person or entity organized, appointed or established by us for or pursuant to the terms of such plan, any person who has acquired beneficial ownership of 15% or more of the outstanding shares of common stock as a result of repurchases of stock by us, certain inadvertent actions by institutional or certain other stockholders as of October 22, 2004, or any person who has entered into any agreement or arrangement with us or any subsidiary of ours for an acquisition transaction.

         In the event that a person becomes an acquiring person (except pursuant to an offer for all outstanding shares of common stock which the independent directors determine to be fair to and otherwise in our best interests and in the best interests of our stockholders), each holder of a right will thereafter have the right to receive, upon exercise, common stock (or, in certain circumstances, cash, property or other securities of the company) having a calculated value equal to two times the exercise price of the right. Notwithstanding the foregoing, following the occurrence of such event, all rights that are, or (under certain circumstances specified in the rights agreement) were, beneficially owned by an acquiring person and certain related persons and transferees will be null and void. However, rights are not exercisable following the occurrence of such event until such time as the rights are no longer redeemable as set forth below.

         At any time prior to the tenth day following the stock acquisition date, we may redeem the rights, in whole, but not in part, at a price of $0.0l per right.

         Until a right is exercised, the holder thereof, as such, will have no rights as a stockholder, including without limitation, the right to vote or to receive dividends.

         In general, the rights agreement may be amended by our board of directors (1) prior to the distribution date in any manner, and (2) on or after the distribution date in certain respects including (a) to shorten or

lengthen at any time period and (b) in a manner not adverse to the interests of rights holders. However, amendments extending the redemption period must be made while the rights are still redeemable.

         The rights have certain anti-takeover effects and will cause substantial dilution to a person or group that attempts to acquire us on terms not approved by our board of directors. The rights should not interfere with any merger or other business combination approved by our board of directors, since our board of directors may redeem the rights as provided above.

Section 203 of Delaware General Corporation Law

         We are subject to the “business combination” statute of the DGCL. In general, such statute prohibits a publicly held Delaware corporation from engaging in a “business combination” with any “interested stockholder” for a period of three years after the date of the transaction in which the person became an “interested stockholder,” unless:

         (1)            such transaction is approved by our board of directors prior to the date the interested stockholder obtains such status,

         (2)            upon consummation of such transaction, the “interested stockholder” beneficially owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the number of shares outstanding those shares owned by (a) persons who are directors and also officers and (b) employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer, or

         (3)            the “business combination” is approved by our board of directors and authorized at an annual or special meeting of stockholders by the affirmative vote of at least 66²/3% of the outstanding voting stock which is not owned by the “interested stockholder.”

         A “business combination” includes mergers, asset sales and other transactions resulting in financial benefit to the “interested stockholder.” An “interested stockholder” is a person who, together with affiliates and associates, owns (or within three years, did own) beneficially 15% or more of a corporation’s voting stock. The statute could prohibit or delay mergers or other takeover or change in control attempts with respect to us and, accordingly, may discourage attempts to acquire us.

Certain Effects of Authorized But Unissued Stock

         Our authorized but unissued shares of common stock and preferred stock may be issued without additional stockholder approval and may be utilized for a variety of corporate purposes, including future offerings to raise additional capital or to facilitate corporate acquisitions.

         The issuance of preferred stock could have the effect of delaying or preventing a change in control of us. The issuance of preferred stock could decrease the amount of earnings and assets available for distribution to holders of our common stock or could adversely affect the rights and powers, including voting rights, of such holders. In certain circumstances, such issuance could have the effect of decreasing the market price of our common stock.

         One of the effects of the existence of unissued and unreserved common stock or preferred stock may be to enable our board of directors to issue shares to persons friendly to current management, which could render more difficult or discourage an attempt to obtain control of us by means of a merger, tender offer, proxy contest or otherwise, and thereby protect the continuity of management. Such, additional shares also could be used to dilute the stock ownership of persons seeking to obtain control of us.

         We plan to issue additional shares of common stock (1) in connection with our employee benefit plans and (2) upon conversion of our trust securities. We do not currently have any plans to issue shares of preferred stock, although 10,000,000 shares of Series A Preferred Stock have been designated pursuant to our rights agreement.

Limitation of Liability of Directors

         Our restated certificate of incorporation contains a provision that limits the liability of our directors for monetary damages for breach of fiduciary duty as a director to the fullest extent permitted by the Delaware General Corporation Law. Such limitation does not, however, affect the liability of a director (1) for any breach of the director’s duty of loyalty to us or our stockholders, (2) for acts or omissions not in good faith or that involve intentional misconduct or a knowing violation of law, (3) in respect of certain unlawful dividend payments or stock redemptions or purchases and (4) for any transaction from which the director derives an improper personal benefit. The effect of this provision is to eliminate our rights and the rights of our stockholders (through stockholders’ derivative suits) to recover monetary damages against a director for breach of the fiduciary duty of care as a director (including breaches resulting from negligent or grossly negligent behavior) except in the situations described in clauses (1) through (4) above. This provision does not limit or eliminate our rights or the rights of our stockholders to seek non-monetary relief such as an injunction or rescission in the event of a breach of a director’s duty of care. In addition, our directors and officers have indemnification protection.

Transfer Agent and Registrar

         The Bank of New York acts as transfer agent and registrar of our common stock.

Listing

         Our common stock is listed on the New York Stock Exchange under the symbol “MCK”.

DESCRIPTION OF DEPOSITARY SHARES

The following description of the depositary shares does not purport to be complete and is subject to and qualified in its entirety by the Deposit Agreement and the depositary receipt relating to the preferred stock that is attached to the Deposit Agreement. You should read these documents as they, and not this description, define your rights as a holder of depositary shares. Forms of these documents have been filed with the SEC as an exhibit to the registration statement of which this prospectus is a part.

General

         If we elect to offer fractional interests in shares of preferred stock, we will provide for the issuance by a depositary to the public of receipts for depositary shares. Each depositary share will represent fractional interests of preferred stock. We will deposit the shares of preferred stock underlying the depositary shares under a Deposit Agreement between us and a bank or trust company selected by us. The bank or trust company must have its principal office in the United States and a combined capital and surplus of at least $50 million. The depositary receipts will evidence the depositary shares issued under the Deposit Agreement.

         The Deposit Agreement will contain terms applicable to the holders of depositary shares in addition to the terms stated in the depositary receipts. Each owner of depositary shares will be entitled to all the rights and preferences of the preferred stock underlying the depositary shares in proportion to the applicable fractional interest in the underlying shares of preferred stock. The depositary will issue the depositary receipts to individuals purchasing the fractional interests in shares of the related preferred stock according to the terms of the offering described in a prospectus supplement.

Dividends and Other Distributions

         The depositary will distribute all cash dividends or other cash distributions received for the preferred stock to the entitled record holders of depositary shares in proportion to the number of depositary shares that the holder owns on the relevant record date. The depositary will distribute only an amount that can be distributed without attributing to any holder of depositary shares a fraction of one cent. The depositary will add the undistributed balance to and treat it as part of the next sum received by the depositary for distribution to holders of depositary shares.

         If there is a non-cash distribution, the depositary will distribute property received by it to the entitled record holders of depositary shares, in proportion, insofar as possible, to the number of depositary shares owned by the holders, unless the depositary determines, after consultation with us, that it is not feasible to make such distribution. If this occurs, the depositary may, with our approval, sell such property and distribute

the net proceeds from the sale to the holders. The Deposit Agreement also will contain provisions relating to how any subscription or similar rights that we may offer to holders of the preferred stock will be available to the holders of the depositary shares.

Conversion, Exchange and Redemption

         If any series of preferred stock underlying the depositary shares may be converted or exchanged, each record holder of depositary receipts will have the right or obligation to convert or exchange the depositary shares represented by the depositary receipts.

         Whenever we redeem shares of preferred stock held by the depositary, the depositary will redeem, at the same time, the number of depositary shares representing the preferred stock. The depositary will redeem the depositary shares from the proceeds it receives from the corresponding redemption, in whole or in part, of the applicable series of preferred stock. The depositary will mail notice of redemption to the record holders of the depositary shares that are to be redeemed between 30 and 60 days before the date fixed for redemption. The redemption price per depositary share will be equal to the applicable fraction of the redemption price per share on the applicable series of preferred stock. If less than all the depositary shares are to be redeemed, the depositary will select which shares to be redeemed by lot, proportionate allocation or any other method.

         After the date fixed for redemption, the depositary shares called for redemption will no longer be outstanding. When the depositary shares are no longer outstanding, all rights of the holders will end, except the right to receive money, securities or other property payable upon redemption.

Voting

         When the depositary receives notice of a meeting at which the holders of the preferred stock are entitled to vote, the depositary will mail the particulars of the meeting to the record holders of the depositary shares. Each record holder of depositary shares on the record date may instruct the depositary on how to vote the shares of preferred stock underlying the holder’s depositary shares. The depositary will try, if practical, to vote the number of shares of preferred stock underlying the depositary shares according to the instructions. The depositary will abstain from voting shares of the preferred stock to the extent it does not receive specific instructions from the holders of depositary shares representing such preferred stock. We will agree to take all reasonable action requested by the depositary to enable it to vote as instructed.

Record Date

         Whenever (1) any cash dividend or other cash distribution shall become payable, any distribution other than cash shall be made, or any rights, preferences or privileges shall be offered with respect to the preferred stock, or (2) the depositary shall receive notice of any meeting at which holders of preferred stock are entitled to vote or of which holders of preferred stock are entitled to notice, or of the mandatory conversion of or any election on our part to call for the redemption of any preferred stock, the depositary shall in each such instance fix a record date (which shall be the same as the record date for the preferred stock) for the determination of the holders of depositary receipts (x) who shall be entitled to receive such dividend, distribution, rights, preferences or privileges or the net proceeds of the sale thereof or (y) who shall be entitled to give instructions for the exercise of voting rights at any such meeting or to receive notice of such meeting or of such redemption or conversion, subject to the provisions of the Deposit Agreement.

Amendments

         We and the depositary may agree to amend the Deposit Agreement and the depositary receipt evidencing the depositary shares. Any amendment that (a) imposes or increases certain fees, taxes or other charges payable by the holders of the depositary shares as described in the Deposit Agreement or that (b) otherwise prejudices any substantial existing right of holders of depositary shares, will not take effect until 30 days after the depositary has mailed notice of the amendment to the record holders of depositary shares. Any holder of depositary shares that continues to hold its shares at the end of the 30-day period will be deemed to have agreed to the amendment.

Termination

         We may direct the depositary to terminate the Deposit Agreement by mailing a notice of termination to holders of depositary shares at least 30 days prior to termination. In addition, a Deposit Agreement will automatically terminate if:

         The depositary may likewise terminate the Deposit Agreement if at any time 60 days shall have expired after the depositary shall have delivered to us a written notice of its election to resign and a successor depositary shall not have been appointed and accepted its appointment. If any depositary receipts remain outstanding after the date of termination, the depositary thereafter will discontinue the transfer of depositary receipts, will suspend the distribution of dividends to the holders thereof, and will not give any further notices (other than notice of such termination) or perform any further acts under the Deposit Agreement except as provided below and except that the depositary will continue (1) to collect dividends on the preferred stock and any other distributions with respect thereto and (2) to deliver the preferred stock together with such dividends and distributions and the net proceeds of any sales of rights, preferences, privileges or other property, without liability for interest thereon, in exchange for depositary receipts surrendered. At any time after the expiration of two years from the date of termination, the depositary may sell the preferred stock then held by it at public or private sales, at such place or places and upon such terms as it deems proper and may thereafter hold the net proceeds of any such sale, together with any money and other property then held by it, without liability for interest thereon, for the pro rata benefit of the holders of depositary receipts which have not been surrendered.

Payment of Fees and Expenses

         We will pay all fees, charges and expenses of the depositary, including the initial deposit of the preferred stock and any redemption of the preferred stock. Holders of depositary shares will pay transfer and other taxes and governmental charges and any other charges as are stated in the Deposit Agreement for their accounts.

Resignation and Removal of Depositary

         At any time, the depositary may resign by delivering notice to us, and we may remove the depositary. Resignations or removals will take effect upon the appointment of a successor depositary and its acceptance of the appointment. The successor depositary must be appointed within 60 days after delivery of the notice of resignation or removal and must be a bank or trust company having its principal office in the United States and having a combined capital and surplus of at least $50 million.

Reports

         The depositary will forward to the holders of depositary shares all reports and communications from us that are delivered to the depositary and that we are required by law, the rules of an applicable securities exchange or our restated certificate of incorporation to furnish to the holders of the preferred stock. Neither we nor the depositary will be liable if the depositary is prevented or delayed by law or any circumstances beyond its control in performing its obligations under the Deposit Agreement. The Deposit Agreement limits our obligations and the depositary’s obligations to performance in good faith of the duties stated in the Deposit Agreement. Neither we nor the depositary will be obligated to prosecute or defend any legal proceeding connected with any depositary shares or preferred stock unless the holders of depositary shares requesting us to do so furnish us with satisfactory indemnity. In performing our obligations, we and the depositary may rely upon the written advice of our counsel or accountants, on any information that competent people provide to us and on documents that we believe are genuine.

DESCRIPTION OF DEBT SECURITIES

         The following descriptions of the debt securities do not purport to be complete and are subject to and qualified in their entirety by reference to the indenture, a form of which has been filed with the SEC as an exhibit to the registration statement of which this prospectus is a part. Any future supplemental indenture or

similar document also will be so filed. You should read the indenture and any supplemental indenture or similar document because they, and not this description, define your rights as holder of our debt securities. All capitalized terms have the meanings specified in the indenture.

         We may issue, from time to time, debt securities, in one or more series, that will consist of either our senior debt (“Senior Debt Securities”), our senior subordinated debt (“Senior Subordinated Debt Securities”), our subordinated debt (“Subordinated Debt Securities”) or our junior subordinated debt (“Junior Subordinated Debt Securities” and, together with the Senior Subordinated Debt Securities and the Subordinated Debt Securities, the “Subordinated Securities”). The debt securities we offer will be issued under an indenture between us and The Bank of New York Trust Company, N.A., acting as trustee. Debt securities, whether senior, senior subordinated, subordinated or junior subordinated, may be issued as convertible debt securities or exchangeable debt securities.

General Terms of the Indenture

         The indenture does not limit the amount of debt securities that we may issue. It provides that we may issue debt securities up to the principal amount that we may authorize and may be in any currency or currency unit designated by us. Except for the limitations on consolidation, merger and sale of all or substantially all of our assets contained in the indenture, the terms of the indenture do not contain any covenants or other provisions designed to afford holders of any debt securities protection with respect to our operations, financial condition or transactions involving us.

         We may issue the debt securities issued under the indenture as “discount securities,” which means they may be sold at a discount below their stated principal amount. These debt securities, as well as other debt securities that are not issued at a discount, may, for U.S. federal income tax purposes, be treated as if they were issued with “original issue discount,” or “OID,” because of interest payment and other characteristics. Special U.S. federal income tax considerations applicable to debt securities issued with original issue discount will be described in more detail in any applicable prospectus supplement.

         The applicable prospectus supplement for a series of debt securities that we issue will describe, among other things, the following terms of the offered debt securities:

         The applicable prospectus supplement will set forth certain U.S. federal income tax considerations for holders of any debt securities and the securities exchange or quotation system on which any debt securities are listed or quoted, if any.

         Debt securities issued by us will be structurally subordinated to all indebtedness and other liabilities of our subsidiaries, except to the extent any such subsidiary guarantees or is otherwise obligated to make payment on such debt securities.

         Unless otherwise provided in the applicable prospectus supplement, all securities of any one series need not be issued at the same time and may be issued from time to time without consent of any holder.

Senior Debt Securities

         Payment of the principal of, premium, if any, and interest on Senior Debt Securities will rank on a parity with all of our other unsecured and unsubordinated debt.

Senior Subordinated Debt Securities

         Payment of the principal of, premium, if any, and interest on Senior Subordinated Debt Securities will be junior in right of payment to the prior payment in full of all of our unsubordinated debt. We will set forth in the applicable prospectus supplement relating to any Senior Subordinated Debt Securities the subordination terms of such securities as well as the aggregate amount of outstanding debt, as of the most recent practicable date, that by its terms would be senior to the Senior Subordinated Debt Securities. We will also set forth in such prospectus supplement limitations, if any, on issuance of additional senior debt.

Subordinated Debt Securities

         Payment of the principal of, premium, if any, and interest on Subordinated Debt Securities will be subordinated and junior in right of payment to the prior payment in full of all of our senior and senior subordinated debt. We will set forth in the applicable prospectus supplement relating to any Subordinated Debt Securities the subordination terms of such securities as well as the aggregate amount of outstanding indebtedness, as of the most recent practicable date, that by its terms would be senior to the Subordinated Debt Securities. We will also set forth in such prospectus supplement limitations, if any, on issuance of additional senior debt.

Junior Subordinated Debt Securities

         Payment of the principal of, premium, if any, and interest on Junior Subordinated Debt Securities will be subordinated and junior in right of payment to the prior payment in full of all of our senior, senior subordinated and subordinated debt. We will set forth in the applicable prospectus supplement relating to any Junior Subordinated Debt Securities the subordination terms of such securities as well as the aggregate amount of outstanding debt, as of the most recent practicable date, that by its terms would be senior to the Junior

Subordinated Debt Securities. We will also set forth in such prospectus supplement limitations, if any, on issuance of additional senior debt.

Conversion or Exchange Rights

         Debt securities may be convertible into or exchangeable for other securities or property of McKesson. The terms and conditions of conversion or exchange will be set forth in the applicable prospectus supplement. The terms will include, among others, the following:

Consolidation, Merger or Sale

         We cannot consolidate or merge with or into, or transfer or lease all or substantially all of our assets to, any person unless (a) we will be the continuing corporation or (b) the successor corporation or person to which our assets are transferred or leased is a corporation organized under the laws of the United States, any state of the United States or the District of Columbia and it expressly assumes our obligations on the debt securities and under the indenture. In addition, we cannot effect such a transaction unless immediately after giving effect to such transaction, no default or event of default under the indenture shall have occurred and be continuing. Subject to certain exceptions, when the person to whom our assets are transferred or leased has assumed our obligations under the debt securities and the indenture, we shall be discharged from all our obligations under the debt securities and the indenture, except in limited circumstances.

         This covenant would not apply to any recapitalization transaction, a change of control of McKesson or a highly leveraged transaction, unless the transaction or change of control were structured to include a merger or consolidation or transfer or lease of all or substantially all of our assets.

Events of Default

         Unless otherwise indicated, the term “Event of Default,” when used in the indenture, means any of the following:

         An Event of Default for a particular series of debt securities does not necessarily constitute an Event of Default for any other series of debt securities issued under the indenture. If an Event of Default relating to the payment of interest, principal or any sinking fund installment involving any series of debt securities has occurred and is continuing, the trustee or the holders of not less than 25% in aggregate principal amount of the debt securities of each affected series may declare the entire principal of all the debt securities of that series to be due and payable immediately.

         If an Event of Default relating to the performance of other covenants occurs and is continuing for a period of 90 days after notice of such, or if any other Event of Default occurs and is continuing involving all of the series of Senior Debt Securities, then the trustee or the holders of not less than 25% in aggregate principal amount of all of the series of Senior Debt Securities may declare the entire principal amount of all of the series of Senior Debt Securities due and payable immediately.

         Similarly, if an Event of Default relating to the performance of other covenants occurs and is continuing for a period of 90 days after notice of such, or if any other Event of Default occurs and is continuing involving all of the series of Subordinated Securities, then the trustee or the holders of not less than 25% in aggregate principal amount of all of the series of Subordinated Securities may declare the entire principal amount of all of the series of Subordinated Securities due and payable immediately.

         If, however, the Event of Default relating to the performance of other covenants or any other Event of Default that has occurred and is continuing is for less than all of the series of Senior Debt Securities or Subordinated Securities, as the case may be, then, the trustee or the holders of not less than 25% in aggregate principal amount of each affected series of the Senior Debt Securities or the Subordinated Securities, as the case may be, may declare the entire principal amount of all debt securities of such affected series due and payable immediately. The holders of not less than a majority in aggregate principal amount of the debt securities of a series may, after satisfying conditions, rescind and annul any of the above-described declarations and consequences involving the series.

         If an Event of Default relating to events in bankruptcy, insolvency or reorganization of McKesson occurs and is continuing, then the principal amount of all of the debt securities outstanding, and any accrued interest, will automatically become due and payable immediately, without any declaration or other act by the trustee or any holder.

         The indenture imposes limitations on suits brought by holders of debt securities against us. Except as provided below, no holder of debt securities of any series may institute any action against us under the indenture unless:

         Notwithstanding the foregoing, each holder of debt securities of any series has the right, which is absolute and unconditional, to receive payment of the principal of and premium and interest, if any, on such debt securities when due and to institute suit for the enforcement of any such payment, and such rights may not be impaired without the consent of that holder of debt securities.

         We will be required to file annually with the Trustee a certificate, signed by an officer of McKesson, stating whether or not the officer knows of any default by us in the performance, observance or fulfillment of any condition or covenant of the indenture.

Registered Global Securities

         We may issue the debt securities of a series in whole or in part in the form of one or more fully registered global securities that we will deposit with a depositary or with a nominee for a depositary identified in the applicable prospectus supplement and registered in the name of such depositary or nominee. In such case, we will issue one or more registered global securities denominated in an amount equal to the aggregate principal amount of all of the debt securities of the series to be issued and represented by such registered global security or securities.

         Unless and until it is exchanged in whole or in part for debt securities in definitive registered form, a registered global security may not be transferred except as a whole:

         The prospectus supplement relating to a series of debt securities will describe the specific terms of the depositary arrangement with respect to any portion of such series represented by a registered global security. We anticipate that the following provisions will apply to all depositary arrangements for debt securities:

         The laws of some states may require that certain purchasers of securities take physical delivery of the securities in definitive form. These laws may limit the ability of those persons to own, transfer or pledge beneficial interests in registered global securities.

         So long as the depositary for a registered global security, or its nominee, is the registered owner of the registered global security, the depositary or the nominee, as the case may be, will be considered the sole owner or holder of the debt securities represented by the registered global security for all purposes under the indenture. Except as set forth below, owners of beneficial interests in a registered global security:

         Accordingly, each person owning a beneficial interest in a registered global security must rely on the procedures of the depositary for the registered global security and, if the person is not a participant, on the procedures of a participant through which the person owns its interest, to exercise any rights of a holder under the indenture.

         We understand that under existing industry practices, if we request any action of holders or if an owner of a beneficial interest in a registered global security desires to give or take any action that a holder is entitled to give or take under the indenture, the depositary for the registered global security would authorize the participants holding the relevant beneficial interests to give or take the action, and those participants would authorize beneficial owners owning through those participants to give or take the action or would otherwise act upon the instructions of beneficial owners holding through them.

         We will make payments of principal and premium, if any, and interest, if any, on debt securities represented by a registered global security registered in the name of a depositary or its nominee to the depositary or its nominee, as the case may be, as the registered owners of the registered global security. None

of McKesson, the trustee or any other agent of McKesson or the trustee will be responsible or liable for any aspect of the records relating to, or payments made on account of, beneficial ownership interests in the registered global security or for maintaining, supervising or reviewing any records relating to the beneficial ownership interests.

         We expect that the depositary for any debt securities represented by a registered global security, upon receipt of any payments of principal and premium, if any, and interest, if any, in respect of the registered global security, will immediately credit participants’ accounts with payments in amounts proportionate to their respective beneficial interests in the registered global security as shown on the records of the depositary. We also expect that standing customer instructions and customary practices will govern payments by participants to owners of beneficial interests in the registered global security held through the participants, as is now the case with the securities held for the accounts of customers in bearer form or registered in “street name.” We also expect that any of these payments will be the responsibility of the participants.

         If the depositary for any debt securities represented by a registered global security is at any time unwilling or unable to continue as depositary or ceases to be a clearing agency registered under the Exchange Act, we will appoint an eligible successor depositary. If we fail to appoint an eligible successor depositary within 90 days, we will issue the debt securities in definitive form in exchange for the registered global security. In addition, we may at any time and in our sole discretion decide not to have any of the debt securities of a series represented by one or more registered global securities. In such event, we will issue debt securities of that series in a definitive form in exchange for all of the registered global securities representing the debt securities. The trustee will register any debt securities issued in definitive form in exchange for a registered global security in such name or names as the depositary, based upon instructions from its participants, shall instruct the trustee.

         We may also issue bearer debt securities of a series in the form of one or more global securities, referred to as “bearer global securities.” We will deposit these bearer global securities with a common depositary for Euroclear System and Clearstream Bank Luxembourg, Societe Anonyme, or with a nominee for the depositary identified in the prospectus supplement relating to that series. The prospectus supplement relating to a series of debt securities represented by a bearer global security will describe the specific terms and procedures, including the specific terms of the depositary arrangement and any specific procedures for the issuance of debt securities in definitive form in exchange for a bearer global security, with respect to the portion of the series represented by a bearer global security.

Discharge, Defeasance and Covenant Defeasance

         We can discharge or defease our obligations under the indenture as set forth below. Unless otherwise set forth in the applicable prospectus supplement, the subordination provisions applicable to any Subordinated Securities will be expressly made subject to the discharge and defeasance provisions of the indenture.

         We may discharge our obligations to holders of any series of debt securities that have not already been delivered to the trustee for cancellation and that have either become due and payable or are by their terms to become due and payable within one year (or are scheduled for redemption within one year). We may effect a discharge by irrevocably depositing with the trustee cash or U.S. government obligations, as trust funds, in an amount certified to be sufficient to pay when due, whether at maturity, upon redemption or otherwise, the principal of, premium, if any, and interest on the debt securities and any mandatory sinking fund payments.

         Unless otherwise provided in the applicable prospectus supplement, we may also discharge any and all of our obligations to holders of any series of debt securities at any time (“legal defeasance”). We also may be released from the obligations imposed by any covenants of any outstanding series of debt securities and provisions of the indenture, and we may omit to comply with those covenants without creating an Event of Default (“covenant defeasance”). We may effect defeasance and covenant defeasance only if, among other things:

         Although we may discharge or defease our obligations under the indenture as described in the two preceding paragraphs, we may not avoid, among other things, our duty to register the transfer or exchange of any series of debt securities, to replace any temporary, mutilated, destroyed, lost or stolen series of debt securities or to maintain an office or agency in respect of any series of debt securities.

Modification of the Indenture

         The indenture provides that we and the trustee may enter into supplemental indentures without the consent of the holders of debt securities to:

         The indenture also provides that we and the trustee may, with the consent of the holders of not less than a majority in aggregate principal amount of debt securities of all series of Senior Debt Securities or Subordinated Securities, as the case may be, then outstanding and affected (voting as one class), add any provisions to, or change in any manner, eliminate or modify in any way the provisions of, the indenture or modify in any manner the rights of the holders of the debt securities. We and the trustee may not, however, without the consent of the holder of each outstanding debt security affected thereby:

Concerning the Trustee

         The indenture provides that there may be more than one trustee under the indenture, each with respect to one or more series of debt securities. If there are different trustees for different series of debt securities, each trustee will be a trustee of a trust under the indenture separate and apart from the trust administered by any other trustee under the indenture. Except as otherwise indicated in this prospectus or any prospectus supplement, any action permitted to be taken by a trustee may be taken by such trustee only with respect to the one or more series of debt securities for which it is the trustee under the indenture. Any trustee under the indenture may resign or be removed with respect to one or more series of debt securities. All payments of principal of, premium, if any, and interest on, and all registration, transfer, exchange, authentication and delivery (including authentication and delivery on original issuance of the debt securities) of, the debt securities of a series will be effected by the trustee with respect to that series at an office designated by the trustee in New York, New York.

         The indenture contains limitations on the right of the trustee, should it become a creditor of McKesson, to obtain payment of claims in some cases or to realize on certain property received in respect of any such claim as security or otherwise. The trustee may engage in other transactions. If it acquires any conflicting interest relating to any duties with respect to the debt securities, however, it must eliminate the conflict or resign as trustee.

         The holders of a majority in aggregate principal amount of any series of debt securities then outstanding will have the right to direct the time, method and place of conducting any proceeding for exercising any remedy available to the trustee with respect to such series of debt securities, provided that the direction would not conflict with any rule of law or with the indenture, would not be unduly prejudicial to the rights of another holder of the debt securities, and would not involve any trustee in personal liability. The indenture provides that in case an Event of Default shall occur and be known to any trustee and not be cured, the trustee must use the same degree of care as a prudent person would use in the conduct of his or her own affairs in the exercise of the trustee’s power. Subject to these provisions, the trustee will be under no obligation to exercise any of its rights or powers under the indenture at the request of any of the holders of the debt securities, unless they shall have offered to the trustee security and indemnity satisfactory to the trustee.

No Individual Liability of Incorporators, Stockholders, Officers or Directors

         The indenture provides that no incorporator and no past, present or future stockholder, officer or director, of McKesson or any successor corporation in their capacity as such shall have any individual liability for any of our obligations, covenants or agreements under the debt securities or the indenture.

Governing Law

         The indenture and the debt securities will be governed by, and construed in accordance with, the laws of the State of New York, including, without limitation, Sections 5-1401 and 5-1402 of the New York General Obligations Law and New York Civil Practice Law and Rules 327(b).

DESCRIPTION OF WARRANTS

General

         We may issue debt warrants for the purchase of debt securities or stock warrants for the purchase of preferred stock or common stock.

         The warrants will be issued under warrant agreements to be entered into between us and a bank or trust company, as warrant agent, all to be set forth in the applicable prospectus supplement relating to any or all warrants in respect of which this prospectus is being delivered. Copies of the form of agreement for each warrant, including the forms of certificates representing the warrants reflecting the provisions to be included in such agreements that will be entered into with respect to the particular offerings of each type of warrant are filed as exhibits to the registration statement of which this prospectus is a part.

         The following description sets forth certain general terms and provisions of the warrants to which any prospectus supplement may relate. The particular terms of the warrants to which any prospectus supplement may relate and the extent, if any, to which such general provisions may apply to the warrants so offered will be described in the applicable prospectus supplement. The following summary of certain provisions of the warrants, warrant agreements and warrant certificates does not purport to be complete and is subject to, and is qualified in its entirety by express reference to, all the provisions of the warrant agreements and warrant certificates, including the definitions therein of certain terms.

Debt Warrants

         General. Reference is made to the applicable prospectus supplement for the terms of debt warrants in respect of which this prospectus is being delivered, the debt securities warrant agreement relating to such debt warrants and the debt warrant certificates representing such debt warrants, including the following:

         The debt warrant certificates will be exchangeable for new debt warrant certificates of different denominations and debt warrants may be exercised at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement. Prior to the exercise of their debt warrants, holders of debt warrants will not have any of the rights of holders of the debt securities purchasable upon such exercise and will not be entitled to any payments of principal and premium, if any, and interest, if any, on the debt securities purchasable upon such exercise.

         Exercise of Debt Warrants. Each debt warrant will entitle the holder to purchase for cash such principal amount of debt securities at such exercise price as shall in each case be set forth in, or be

determinable as set forth in, the applicable prospectus supplement relating to the debt warrants offered thereby. Unless otherwise specified in the applicable prospectus supplement, debt warrants may be exercised at any time up to 5:00 p.m., New York City time, on the expiration date set forth in the applicable prospectus supplement. After 5:00 p.m., New York City time, on the expiration date, unexercised debt warrants will become void.

         Debt warrants may be exercised as set forth in the applicable prospectus supplement relating to the debt warrants. Upon receipt of payment and the debt warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will, as soon as practicable, forward the debt securities purchasable upon such exercise. If less than all of the debt warrants represented by such debt warrant certificate are exercised, a new debt warrant certificate will be issued for the remaining amount of debt warrants.

Stock Warrants

         General. Reference is made to the applicable prospectus supplement for the terms of stock warrants in respect of which this prospectus is being delivered, the stock warrant agreement relating to such stock warrants and the stock warrant certificates representing such stock warrants, including the following:

         The stock warrant certificates will be exchangeable for new stock warrant certificates of different denominations and stock warrants may be exercised at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement. Prior to the exercise of their stock warrants, holders of stock warrants will not have any of the rights of holders of shares of capital stock purchasable upon such exercise, and will not be entitled to any dividend payments on such capital stock purchasable upon such exercise.

         Exercise of Stock Warrants. Each stock warrant will entitle the holder to purchase for cash such number of shares of preferred stock or common stock, as the case may be, at such exercise price as shall in each case be set forth in, or be determinable as set forth in, the applicable prospectus supplement relating to the stock warrants offered thereby. Unless otherwise specified in the applicable prospectus supplement, stock warrants may be exercised at any time up to 5:00 p.m., New York City time, on the expiration date set forth in the applicable prospectus supplement. After 5:00 p.m., New York City time, on the expiration date, unexercised stock warrants will become void.

         Stock warrants may be exercised as set forth in the applicable prospectus supplement relating thereto. Upon receipt of payment and the stock warrant certificates properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement,

we will, as soon as practicable, forward a certificate representing the number of shares of capital stock purchasable upon such exercise. If less than all of the stock warrants represented by such stock warrant certificate are exercised, a new stock warrant certificate will be issued for the remaining amount of stock warrants.

DESCRIPTION OF STOCK PURCHASE CONTRACTS AND STOCK PURCHASE UNITS

         We may issue stock purchase contracts, representing contracts obligating holders to purchase from us, and requiring us to sell to the holders, a specified number of shares of common stock at a future date or dates. The price per share of common stock may be fixed at the time the stock purchase contracts are issued or may be determined by reference to a specific formula set forth in the stock purchase contracts. The stock purchase contracts may be issued separately or as a part of units, or stock purchase units, consisting of a stock purchase contract and either (x) senior debt securities, senior subordinated debt securities, subordinated debt securities or junior subordinated debt securities, or (y) debt obligations of third parties, including U.S. Treasury securities, in each case, securing the holder’s obligations to purchase the common stock under the stock purchase contracts. The stock purchase contracts may require us to make periodic payments to the holders of the stock purchase contracts or vice versa, and such payments may be unsecured or prefunded on some basis. The stock purchase contracts may require holders to secure their obligations thereunder in a specified manner and in certain circumstances we may deliver newly issued prepaid stock purchase contracts, or prepaid securities, upon release to a holder of any collateral securing such holder’s obligations under the original stock purchase contract.

         The applicable prospectus supplement will describe the terms of any stock purchase contracts or stock purchase units and, if applicable, prepaid securities. The description in the prospectus supplement will not purport to be complete and will be qualified in its entirety by reference to the stock purchase contracts, the collateral arrangements and depositary arrangements, if applicable, relating to such stock purchase contracts or stock purchase units and, if applicable, the prepaid securities and the document pursuant to which such prepaid securities will be issued.

PLAN OF DISTRIBUTION

         McKesson may sell common stock, preferred stock, depositary shares, debt securities, warrants, stock purchase contracts or stock purchase units in one or more of the following ways from time to time:

         The prospectus supplements relating to an offering of offered securities will set forth the terms of such offering, including:

         Any initial public offering prices, discounts or concessions allowed or reallowed or paid to dealers may be changed from time to time.

         If underwriters are used in the sale, the underwriters will acquire the offered securities for their own account and may resell them from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. The offered securities may be offered either to the public through underwriting syndicates represented by one or more managing underwriters or by one or more underwriters without a syndicate. Unless otherwise set forth in a prospectus supplement, the obligations of the underwriters to purchase any series of securities will be subject to certain conditions precedent, and the underwriters will be obligated to purchase all of such series of securities, if any are purchased.

         In connection with underwritten offerings of the offered securities and in accordance with applicable law and industry practice, underwriters may over-allot or effect transactions that stabilize, maintain or otherwise affect the market price of the offered securities at levels above those that might otherwise prevail in the open market, including by entering stabilizing bids, effecting syndicate covering transactions or imposing penalty bids, each of which is described below.

         These transactions may be effected on the NYSE, in the over-the-counter market, or otherwise. Underwriters are not required to engage in any of these activities, or to continue such activities if commenced.

         If a dealer is used in the sale, McKesson will sell such offered securities to the dealer, as principal. The dealer may then resell the offered securities to the public at varying prices to be determined by that dealer at the time for resale. The names of the dealers and the terms of the transaction will be set forth in the prospectus supplement relating to that transaction.

         Offered securities may be sold directly by McKesson to one or more institutional purchasers, or through agents designated by McKesson from time to time, at a fixed price or prices, which may be changed, or at varying prices determined at the time of sale. Any agent involved in the offer or sale of the offered securities in respect of which this prospectus is delivered will be named, and any commissions payable by McKesson to such agent will be set forth, in the prospectus supplement relating to that offering. Unless otherwise indicated in such prospectus supplement, any such agent will be acting on a best efforts basis for the period of its appointment.

         Underwriters, dealers and agents may be entitled under agreements entered into with us to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments that the underwriters, dealers or agents may be required to make in respect thereof. Underwriters, dealers and agents may be customers of, engage in transactions with, or perform services for us and our affiliates in the ordinary course of business.

         Other than our common stock, which is listed on the New York Stock Exchange, each of the securities issued hereunder will be a new issue of securities, will have no prior trading market, and may or may not be listed on a national securities exchange or the Nasdaq Stock Market. Any common stock sold pursuant to a prospectus supplement will be listed on the New York Stock Exchange, subject to official notice of issuance. Any underwriters to whom McKesson sells securities for public offering and sale may make a market in the securities, but such underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We cannot assure you that there will be a market for the offered securities.

LEGAL MATTERS

         The validity of the securities being offered hereby is being passed upon for McKesson Corporation by Skadden, Arps, Slate, Meagher & Flom LLP, Los Angeles, California.

EXPERTS

         The consolidated financial statements, financial statement schedule and management’s report on the effectiveness of internal control over financial reporting incorporated in this prospectus by reference from McKesson Corporation’s Annual Report on Form 10-K for the year ended March 31, 2005 have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports, which are incorporated herein, and have been so incorporated in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing.

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$                                             

$                                     % Notes due 2013

$                                     % Notes due 2017

Prospectus Supplement

Banc of America Securities LLC

Wachovia Securities

February     , 2007