Form 4 Filed by Pioneer Natural Resources Usa Inc on May 07, 2008

This form 4 (insider trading filing) was submitted to the Securities and Exchange Commission (SEC) by insider Pioneer Natural Resources Usa Inc on May 07, 2008. The CIK number of this insider is 846920. At the time of this reporting, Pioneer Natural Resources Usa Inc is the Other of Pioneer Southwest Energy Partners L.p. . See all insider stock transactions reported by Pioneer Natural Resources Usa Inc and all stock buys, sales, and option exercises made by insiders at Pioneer Southwest Energy Partners L.p. . The stock ticker symbol of Pioneer Southwest Energy Partners L.p. is PSE.

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP 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	OMB APPROVAL OMB Number: 3235-0287 Expires: February 28, 2011 Estimated average burden hours per response 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* PIONEER NATURAL RESOURCES CO (Last) (First) (Middle) 5205 N. O'CONNOR BLVD, SUITE 200 (Street) IRVING TX 75039 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Pioneer Southwest Energy Partners L.P. [ PSE ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) X Other (specify below) Indirect Owner of Gen Partner
	3. Date of Earliest Transaction (Month/Day/Year) 05/06/2008
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

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 Units	05/06/2008		P		20,521,200	A	$19	20,521,200	I	See Footnote ( 1 ) ( 2 )

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 Securities Underlying Derivative Security (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: 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

1. Name and Address of Reporting Person* PIONEER NATURAL RESOURCES CO (Last) (First) (Middle) 5205 N. O'CONNOR BLVD, SUITE 200 (Street) IRVING TX 75039 (City) (State) (Zip)

1. Name and Address of Reporting Person* PIONEER NATURAL RESOURCES USA INC (Last) (First) (Middle) 5205 N. O'CONNOR BLVD., SUITE 200 (Street) IRVING TX 75039 (City) (State) (Zip)

Explanation of Responses:

1. The securities reported on this Form 4 are held directly by Pioneer Natural Resources USA, Inc. ("Pioneer USA"). Pioneer USA is a wholly-owned subsidiary of Pioneer Natural Resources Company ("Pioneer"). Pioneer is an indirect beneficial owner of the reported securities. Pioneer USA is also a direct owner of the general partner of the Issuer.

2. On May 6, 2008, in connection with the Issuer's initial public offering, Pioneer USA contributed a portion of its ownership interest in the operating company to the Issuer in exchange for the reported securities, all in accordance with the Contribution Agreement, dated May 6, 2008, by and among Pioneer USA, the general partner and the Issuer.

Remarks:

	By: Mark H. Kleinman, Vice President	05/07/2008
	Mark H. Kleinman, Vice President	05/06/2008
	** Signature of Reporting Person	Date
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