PSE Pioneer Southwest Energy Partners L.P. Pioneer Southwest Energy Partners Lp

Pioneer Southwest Energy Partners L.P. (�Pioneer Southwest�) (NYSE:PSE) announces a change in the time of its third quarter 2008 earnings conference call and webcast on Wednesday, November 5, 2008 from 11:00 a.m. CT to 9:00 a.m. CT. This change is being made to avoid conflicts with other companies� earnings calls. Instructions on how to listen to the call and view the accompanying presentation are shown below. November 5, 2008 at 9:00 a.m. CT Internet: http://www.pioneersouthwest.com Select �Investors,� then �Earnings Calls & Webcasts� to listen to the discussion and view the presentation. Telephone: Dial (877) 874-1586 (confirmation code: 6541865) five minutes before the call to listen to the discussion. View the presentation via Pioneer Southwest�s internet address above. A replay of the webcast will be archived on Pioneer Southwest�s website. A telephone replay will be available through November 26 by dialing (888) 203-1112, confirmation code: 6541865. Pioneer Southwest is a Delaware limited partnership formed by Pioneer Natural Resources Company to own and acquire oil and gas assets in its area of operations. This area includes onshore Texas and eight counties in the southeast region of New Mexico. Special Notice Regarding Pioneer Natural Resources Company Third Quarter Earnings Call. On Wednesday, November 5, 2008 at 11:00 a.m. CT, Pioneer Natural Resources Company (�PNRC�) will conduct its third quarter 2008 earnings conference call and webcast. Pioneer Southwest was formed by PNRC to own and acquire oil and gas assets in Pioneer Southwest�s area of operations. As such, it is possible that discussion on the PNRC call will include matters regarding Pioneer Southwest. To listen to the PNRC call dial (877) 879-6209, confirmation code: 3324323, five minutes before the call. The accompanying presentation can be viewed at http://www.pxd.com. Select �Investors,� then �Earnings Calls & Webcasts� to listen to the discussion and view the presentation. A replay of the webcast will be archived on PNRC�s website. A telephone replay will be available through November 26 by dialing (888) 203-1112, confirmation code: 3324323.