Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
SHEFFIELD SCOTT D
   2. Issuer Name and Ticker or Trading Symbol
PIONEER NATURAL RESOURCES CO [PXD] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
Chairman & CEO
(Last)
(First)
(Middle)
5205 N. O'CONNOR BLVD., SUITE 200		 3. Date of Earliest Transaction (Month/Day/Year)
03/12/2010
(Street)

IRVING, TX 75039		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock               22,133 (1) I 401(k)
Common Stock 03/12/2010   M   20,000 A $ 24.72 637,309 D  
Common Stock 03/12/2010   S   2,600 D $ 52.1765 634,709 D  
Common Stock 03/12/2010   S   300 D $ 52.195 634,409 D  
Common Stock 03/12/2010   S   1,200 D $ 52.2367 633,209 D  
Common Stock 03/12/2010   S   500 D $ 52.242 632,709 D  
Common Stock 03/12/2010   S   200 D $ 52.2425 632,509 D  
Common Stock 03/12/2010   S   100 D $ 52.245 632,409 D  
Common Stock 03/12/2010   S   2,000 D $ 52.2497 630,409 D  
Common Stock 03/12/2010   S   200 D $ 52.25 630,209 D  
Common Stock 03/12/2010   S   200 D $ 52.255 630,009 D  
Common Stock 03/12/2010   S   800 D $ 52.2594 629,209 D  
Common Stock 03/12/2010   S   200 D $ 52.26 629,009 D  
Common Stock 03/12/2010   S   1,800 D $ 52.2631 627,209 D  
Common Stock 03/12/2010   S   700 D $ 52.27 626,509 D  
Common Stock 03/12/2010   S   900 D $ 52.2711 625,609 D  
Common Stock 03/12/2010   S   926 D $ 52.2804 624,683 D  
Common Stock 03/12/2010   S   100 D $ 52.29 624,583 D  
Common Stock 03/12/2010   S   900 D $ 52.3 623,683 D  
Common Stock 03/12/2010   S   500 D $ 52.32 623,183 D  
Common Stock 03/12/2010   S   500 D $ 52.37 622,683 D  
Common Stock 03/12/2010   S   400 D $ 52.4 622,283 D  

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Non-Qualified Stock Option (right to buy) $ 24.72 03/12/2010   M     20,000 08/12/2005 08/12/2010 Common Stock 20,000 $ 0 0 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
SHEFFIELD SCOTT D
5205 N. O'CONNOR BLVD., SUITE 200
IRVING, TX 75039		       Chairman & CEO  

Signatures

 Mark H. Kleinman, Attorney-in-Fact For Scott D. Sheffield   03/16/2010
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Consists of shares beneficially owned as a result of reporting person's ownership of units in the Pioneer Natural Resources USA, Inc. 401(k) Plan

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