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 *
BAROFFIO JAMES R
  2. Issuer Name and Ticker or Trading Symbol
PIONEER NATURAL RESOURCES CO [PXD]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
5205 N. O'CONNOR BLVD., SUITE 900
3. Date of Earliest Transaction (Month/Day/Year)
05/11/2006
(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 05/11/2006   M   10,000 A $ 10.25 11,912 D  
Common Stock 05/11/2006   S   10,000 D $ 41.81 1,912 D  
Common Stock 05/11/2006   M   1,978 A $ 13.5 13,031 I by Trust (1)
Common Stock 05/11/2006   S   1,978 D $ 41.81 11,053 I by Trust (1)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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) $ 10.25 05/11/2006   M     10,000 05/18/2001 05/18/2006 Common Stock 10,000 $ 10.25 10,000 D  
Non-Qualified Stock Option (right to buy) $ 13.5 05/11/2006   M     1,978 05/18/2001(2) 05/18/2006 Common Stock 1,978 $ 13.5 0 I by Trust (1)

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
BAROFFIO JAMES R
5205 N. O'CONNOR BLVD., SUITE 900
IRVING, TX 75039
  X      

Signatures

 By: Mark H. Kleinman, Attorney-in-Fact For: James R. Baroffio   05/12/2006
**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) Shares held by Baroffio Family Trust, of which James R. Baroffio is Trustee.
(2) One-fourth of the options shall vest at the end of each of the Board's fiscal quarters (with the exception of the quarter ending with the Annual Meeting, which is deemed to end on the day prior to the Annual meeting), are immediately exercisable upon such vesting, and survive for a term of five years from the vest date.

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