The securities litigation firm of Brower Piven, A Professional Corporation, has commenced an investigation into possible breaches of fiduciary duty to current shareholders of Pioneer Southwest Energy Partners L.P. ("Pioneer Southwest" or the "Company") (NYSE: PSE) and other violations of state law by the board of directors of Pioneer Southwest relating to the proposed acquisition of the Company by Pioneer Natural Resources Company ("Pioneer Natural Resources"). The firm's investigation seeks to determine, among other things, whether the board of directors of Pioneer Southwest breached their fiduciary duties by failing to maximize shareholder value.

As stated in the press release announcing the proposed buyout, Pioneer Southwest shareholders will receive 0.2234 shares of Pioneer Natural Resources for each share of common stock they own.

If you currently own common stock of Pioneer Southwest and would like to learn more about the investigation being conducted by Brower Piven, you may email or call Brower Piven, who will, without obligation or cost to you, attempt to answer your questions. You may contact Brower Piven by email at hoffman@browerpiven.com, by calling (410) 415-6616, or at Brower Piven, A Professional Corporation, 1925 Old Valley Road, Stevenson, Maryland 21153. Attorneys at Brower Piven have combined experience litigating securities and other class action cases of over 60 years.

Brower Piven, A Professional Corporation
Stevenson, Maryland
Charles J. Piven, 410-415-6616
hoffman@browerpiven.com