Pioneer Natural Resources Alters Organization of Board of Directors

Pioneer Natural Resources Company and Southeastern Asset Management, Inc. have entered into an agreement that alters the composition of Pioneer's Board of Directors. Southeastern, a value-oriented investment management firm, is Pioneer's largest shareholder and currently holds approximately 23 million shares, or 20% of Pioneer's common stock.

Under the agreement, Pioneer's Board will be reduced from eleven members to ten members, consisting of seven existing Board members and three new directors to be recommended by Southeastern, whose nomination is subject to approval by Pioneer.

Southeastern has proposed for consideration the three individuals to be added to Pioneer's Board of Directors. Concurrently, the Nominating and Governance Committee of Pioneer's Board is identifying the six outside directors who will remain on the Board with Scott Sheffield, Pioneer's Chairman of the Board and Chief Executive Officer. Pioneer expects to complete the process of naming the new and continuing outside directors by June 1, 2009. As a result of this agreement, the Company will reschedule its Annual Meeting (originally scheduled for May 8) to a later date to be announced.

"Southeastern is a valued partner and astute investor, and we appreciate their long-term commitment to our vision and continued success," stated Scott Sheffield, Pioneer's Chairman and CEO. "We have always respected the leadership at Southeastern and welcome their insight and ideas, especially during these difficult and challenging economic times. Recognizing Southeastern's ownership of almost 20% of our outstanding shares, Pioneer's Board and management support their efforts to add three new directors to our Board. We look forward to working together with Southeastern and these new directors to enhance value for all Pioneer shareholders."

O. Mason Hawkins, Chairman of Southeastern Asset Management, Inc., stated, "We believe the newly constituted Board will bring a fresh focus to intelligent hedging and capital allocation to complement Pioneer's operational strengths. We appreciate the efforts of Pioneer's Board and management in working with us to reach mutual agreement on the changes to Pioneer's Board. These actions affirm our common desire to maximize the value of Pioneer's long-lived core assets for shareholders."