SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                  -------------

                                 SCHEDULE 13D/A*
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
            TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO
                                  RULE 13d-2(a)

                    Under the Securities Exchange Act of 1934
                                (Amendment No. 4)

                             Kerr-McGee Corporation
--------------------------------------------------------------------------------
                                (Name of Issuer)

                     Common Stock, par value $1.00 per share
--------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    492386107
--------------------------------------------------------------------------------
                                 (CUSIP Number)

                              Marc Weingarten, Esq.
                            Schulte Roth & Zabel LLP
                                919 Third Avenue
                            New York, New York 10022
                                 (212) 756-2000
--------------------------------------------------------------------------------
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                 April 13, 2005
--------------------------------------------------------------------------------
                          (Date of Event which Requires
                            Filing of This Statement)



         If the filing person has previously filed a statement on Schedule 13G
to report the acquisition that is the subject of this Schedule 13D, and is
filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the
following box. [ ]

         NOTE: Schedules filed in paper format shall include a signed original
and five copies of the schedule, including all exhibits. See Rule 13d-7 for
other parties to whom copies are to be sent.

                         (Continued on following pages)

                               (Page 1 of 6 Pages)

--------------------------

* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

   The information required on the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section of
the Act but shall be subject to all other provisions of the Act (however, see
the Notes).





------------------------------                             ---------------------
CUSIP NO.      492386107              SCHEDULE 13D/A       PAGE 2 OF 6 PAGES
------------------------------                             ---------------------

--------------------------------------------------------------------------------
    1       NAME OF REPORTING PERSON
            I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

                                JANA PARTNERS LLC
--------------------------------------------------------------------------------
    2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*       (a) [ ]
                                                                    (b) [X]

--------------------------------------------------------------------------------
    3       SEC USE ONLY

--------------------------------------------------------------------------------
    4       SOURCE OF FUNDS*

            AF
--------------------------------------------------------------------------------
    5       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED PURSUANT
            TO ITEM 2(d) or 2(e)                                         [ ]

--------------------------------------------------------------------------------
    6       CITIZENSHIP OR PLACE OF ORGANIZATION

            Delaware
--------------------------------------------------------------------------------
                         7      SOLE VOTING POWER

                                4,388,700 (including options to purchase up to
                                1,587,600 Shares) (see Item 5)
                      ----------------------------------------------------------
 NUMBER OF               8      SHARED VOTING POWER
  SHARES
BENEFICIALLY                    -0-
  OWNED BY            ----------------------------------------------------------
    EACH                 9      SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                     4,388,700 (including options to purchase up to
                                1,587,600 Shares) (see Item 5)
                      ----------------------------------------------------------
                         10     SHARED DISPOSITIVE POWER

                                -0-
--------------------------------------------------------------------------------
    11      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

            4,388,700 (including options to purchase up to 1,587,600 Shares)
            (see Item 5)
--------------------------------------------------------------------------------
    12      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
            CERTAIN SHARES*
                                                                             [X]
--------------------------------------------------------------------------------
    13      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            2.7% (see Item 5)
--------------------------------------------------------------------------------
    14      TYPE OF REPORTING PERSON*

            IA
--------------------------------------------------------------------------------
                     * SEE INSTRUCTIONS BEFORE FILLING OUT!





------------------------------                             ---------------------
CUSIP NO.      492386107              SCHEDULE 13D/A       PAGE 3 OF 6 PAGES
------------------------------                             ---------------------

The Schedule 13D filed on March 3, 2005 by Jana Partners LLC, a Delaware limited
liability company (the "Reporting Person"), relating to the common stock, $1.00
par value (the "Shares"), of Kerr-McGee Corporation (the "Issuer"), as
amended by Amendment No. 1 dated March 10, 2005, Amendment No. 2 dated March 24,
2005 and Amendment No. 3 dated April 4, 2005, is hereby amended as set forth
below by this Amendment No. 4 to the Schedule 13D.

ITEM 3.           SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

         Item 3 of the Schedule 13D is hereby amended and restated as follows:

         Of the 4,388,700 Shares reported herein by the Reporting Person,
2,801,100 Shares were acquired at an aggregate purchase price of approximately
$174,730,022.67, and the remaining 1,587,600 Shares represent options to acquire
Shares, which options were acquired at an aggregate purchase price of
approximately $7,265,710.92. The Shares beneficially owned by the Reporting
Person were acquired with investment funds in accounts under management.

ITEM 4.           PURPOSE OF TRANSACTION.

         Item 4 of the Schedule 13D is hereby amended by the addition of the
following:

         On April 13, 2005, the Reporting Person, the Icahn Group and the Issuer
entered into an agreement (the "Agreement"). A copy of the Agreement is attached
hereto as Exhibit F and incorporated herein by reference.

         On April 14, 2005, the Reporting Person and the Icahn Group issued a
press release (the "Press Release"). A copy of the Press Release is attached
hereto as Exhibit G and incorporated herein by reference.


CARL C. ICAHN, BARRY S. ROSENSTEIN AND CERTAIN RELATED PARTIES FILED A
PRELIMINARY PROXY STATEMENT WITH THE SECURITIES AND EXCHANGE COMMISSION ON APRIL
8, 2005 RELATING TO THEIR SOLICITATION OF PROXIES FROM THE STOCKHOLDERS OF
KERR-MCGEE CORPORATION WITH RESPECT TO THE 2005 ANNUAL MEETING OF KERR-MCGEE'S
STOCKHOLDERS. THE PRELIMINARY PROXY STATEMENT CONTAINS DETAILED INFORMATION
REGARDING THE NAMES, AFFILIATIONS AND INTERESTS OF PERSONS WHO MAY BE DEEMED
PARTICIPANTS IN THE SOLICITATION OF PROXIES OF KERR-MCGEE'S STOCKHOLDERS. THESE
PARTIES INTEND TO FILE A DEFINITIVE PROXY STATEMENT AND OTHER RELEVANT DOCUMENTS
WITH THE SECURITIES AND EXCHANGE COMMISSION. SECURITY HOLDERS ARE ADVISED TO
READ THE PROXY STATEMENT AND OTHER RELEVANT DOCUMENTS BECAUSE THEY WILL CONTAIN
IMPORTANT INFORMATION. THE PROXY STATEMENT AND OTHER RELEVANT DOCUMENTS MAY BE
OBTAINED WITHOUT CHARGE FROM THE SECURITIES AND EXCHANGE COMMISSION'S WEBSITE AT
HTTP://WWW.SEC.GOV, AND THE DEFINITIVE PROXY STATEMENT AND A FORM OF PROXY WILL
BE MAILED TO STOCKHOLDERS OF KERR-MCGEE CORPORATION.


ITEM 5.           INTEREST IN SECURITIES OF THE COMPANY.

         Paragraphs (a) and (b) of Item 5 of the Schedule 13D are hereby amended
by the addition of the following:

         (a) The aggregate percentage of Shares reported to be beneficially
owned by the Reporting Person is based upon 163,442,818 Shares outstanding,
which is the total number of Shares outstanding as of March 11, 2005 as reported
in the Issuer's definitive proxy statement on Schedule 14A filed on April 1,
2005.

         As of the close of business on April 13, 2005, the Reporting Person may
be deemed to beneficially own 4,388,700 Shares (including options to purchase up
to 1,587,600 Shares), constituting approximately 2.7% of the Shares outstanding.
Upon information and belief, the Icahn Group, as of the close of business on
April 13, 2005, may be deemed to beneficially own 8,244,100 Shares. Accordingly,
the 12,632,800 Shares that may be deemed to be beneficially owned in the
aggregate by the Reporting Person and the Icahn Group as a "group," as of the
close of business on April 13, 2005, constitutes approximately 7.7% of the
Shares outstanding. The Reporting Person expressly disclaims beneficial
ownership of securities held by the Icahn Group or any person or entity other
than, to the extent of any pecuniary interest therein, the various accounts
under the Reporting Person's management and control.

         (b) The Reporting Person has sole voting and dispositive powers over
the 4,388,700 Shares reported herein (including, if such options are exercised,
the 1,587,600 Shares underlying the options reported herein), which powers are
exercised by the Principals.





------------------------------                             ---------------------
CUSIP NO.      492386107              SCHEDULE 13D/A       PAGE 4 OF 6 PAGES
------------------------------                             ---------------------


ITEM 6.           CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH
                  RESPECT TO SECURITIES OF THE ISSUER.

         Item 6 of the Schedule 13D is hereby amended and restated as follows:

         As set forth below, the Reporting Person holds, as of the close of
business on April 13, 2005, options to acquire 1,587,600 Shares, each of which
was acquired on the open market:


                 Shares
   Date of     Underlying     Exercise Price                     Purchase Price
  Purchase       Options      per Share ($)    Expiration Date   per Option ($)
-------------------------------------------------------------------------------
  02/28/05        73,300         80.00             04/15/05           2.0558
  03/01/05       100,000         80.00             04/15/05           2.7408
  03/02/05        85,100         80.00             04/15/05           3.1693
  03/17/05       352,200         80.00             04/15/05           2.8197
  03/17/05       180,200         75.00             04/15/05           6.7099
  03/17/05       356,600         75.00             04/15/05           6.0286
  03/18/05        58,300         80.00             04/15/05           3.8390
  03/18/05        81,900         75.00             04/15/05           7.0603
  03/21/05        50,000         75.00             04/15/05           7.4114
  03/21/05       100,000         80.00             05/20/05           5.1000
  04/06/05       100,000         75.00             05/20/05           3.7459
  04/07/05        50,000         75.00             05/20/05           3.2400

         As more fully described in Item 4, pursuant to discussions among the
Reporting Person and the Icahn Group, on March 2, 2005 the Icahn Group notified
the Issuer that it proposed to nominate Barry Rosenstein and Carl Icahn for
election to the Issuer's board of directors at the 2005 annual meeting of
stockholders. Representatives of the Reporting Person and the Icahn Group have
suggested various actions to the Issuer that they believe would enhance
stockholder value.

         On or about March 14, 2005, the Issuer filed the Amended Complaint
alleging, among other things, (i) violation of reporting requirements of Section
13(d) of the Act and Rule 13d-1 thereunder, (ii) failure of the Icahn Group's
notification of its intention to nominate Messrs. Rosenstein and Icahn as
directors to comply with the Issuer's By-Law requirements and (iii) violation of
Section 14(a) of the Act and Rule 14a-9 thereunder. The Amended Complaint
sought, among other things, a declaratory judgment that the proposed nominations
of Messrs. Rosenstein and Icahn as directors are invalid. A copy of the Amended
Complaint is attached hereto as Exhibit D.

         The Reporting Person determined to solicit proxies on behalf of Messrs.
Rosenstein and Icahn as candidates for director of the Issuer at the Issuer's
2005 annual meeting of stockholders. Accordingly, a preliminary proxy statement
was filed by the Reporting Person, the Icahn Group and certain related parties
on March 24, 2005 and subsequently amended. The Reporting Person and the Icahn
Group agreed to each pay half of the costs related to the proxy solicitation,
except that each would bear its own legal expenses.

         On April 13, 2005, the Reporting Person, the Icahn Group and the Issuer
entered into an agreement (the "Agreement"). A copy of the Agreement is attached
hereto as Exhibit F and incorporated herein by reference.

         On April 14, 2005, the Reporting Person and the Icahn Group issued a
press release (the "Press Release"). A copy of the Press Release is attached
hereto as Exhibit G and incorporated herein by reference.

         Except as otherwise set forth herein, the Reporting Person does not
have any contract, arrangement, understanding or relationship with any person
with respect to securities of the Issuer.


ITEM 7.           MATERIAL TO BE FILED AS EXHIBITS.

         Item 7 of the Schedule 13D is hereby amended by the addition of the
following:

6. Exhibit F - Agreement among the Reporting Person, the Icahn Group and the
Issuer.

7. Exhibit G - Press Release issued by the Reporting Person and the Icahn Group.






---------------------------                                 -------------------
CUSIP NO.      492386107             SCHEDULE 13D/A         PAGE 5 OF 6 PAGES
---------------------------                                 -------------------

                                   SIGNATURES

      After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Dated:  April 14, 2005


                                           JANA PARTNERS LLC


                                           By: /s/ Barry S. Rosenstein
                                               ---------------------------
                                               Name: Barry S. Rosenstein
                                               Title:   Managing Director


                                           By: /s/ Gary Claar
                                               ---------------------------
                                               Name: Gary Claar
                                               Title:  Managing Director










---------------------------                                 -------------------
CUSIP NO.      492386107             SCHEDULE 13D/A         PAGE 6 OF 6 PAGES
---------------------------                                 -------------------

                                  EXHIBIT INDEX

1. Exhibit A - Letter to the Issuer dated March 3, 2005 (previously filed).

2. Exhibit B - [reserved].

3. Exhibit C - Letter to the Issuer dated March 10, 2005 (previously filed).

4. Exhibit D - Amended Complaint dated March 14, 2005 (previously filed).

5. Exhibit E - Letter to the Issuer dated April 4, 2005 (previously filed).

6. Exhibit F - Agreement among the Reporting Person, the Icahn Group and the
Issuer.

7. Exhibit G - Press Release issued by the Reporting Person and the Icahn Group.