DALLAS–(Business Wire)–
Pioneer Southwest Energy Partners L.P.(“Pioneer Southwest”)(NYSE:PSE) today
announced a cash distribution of $0.50 per unit on Pioneer Southwest’s
outstanding common units for the quarter ended June 30, 2010. The distribution
is payable August 12, 2010, to unitholders of record at the close of business on
August 4, 2010.

Pioneer Southwest is a Delaware limited partnership, headquartered in Dallas,
Texas, with current production and drilling operations in the Spraberry field in
West Texas. For more information, visit www.pioneersouthwest.com.

Pioneer Southwest Energy Partners L.P.
Investors
Frank Hopkins, 972-969-4065
or
Nolan Badders, 972-969-3955
or
Media and Public Affairs
Susan Spratlen, 972-969-4018
or
Suzanne Hicks, 972-969-4020

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