UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549



                                    FORM 8-K
                                 CURRENT REPORT

                         Pursuant to Section 13 or 15(d)
                     of the Securities Exchange Act of 1934


      Date of Report (Date of earliest event reported): September 16, 2005



                        PIONEER NATURAL RESOURCES COMPANY
             ------------------------------------------------------
             (Exact name of registrant as specified in its charter)


          Delaware                    1-13245               75-2702753
----------------------------       ------------       ----------------------
(State or other jurisdiction       (Commission           (I.R.S. Employer
      of incorporation)            File Number)       Identification Number)


5205 N. O'Connor Blvd., Suite 900, Irving, Texas              75039
------------------------------------------------            ----------
    (Address of principal executive offices)                (Zip code)


       Registrant's telephone number, including area code: (972) 444-9001

                                 Not applicable
          -------------------------------------------------------------
          (Former name or former address, if changed since last report)


Check  the  appropriate  box  below  if the  Form  8-K  filing  is  intended  to
simultaneously  satisfy the filing obligation of the Registrant under any of the
following provisions:

[ ] Written communications pursuant to Rule 425 under the Securities Act (17 CFR
    230.425)
[ ] Soliciting material pursuant to Rule 14a-12  under the  Exchange Act (17 CFR
    240.14a-12)
[ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange
    Act (17 CFR 240.14d-2(b))
[ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange
    Act (17 CFR 240.13e-4(c))







Item 1.01. Entry into a Material Definitive Agreement

On September 16, 2005, Pioneer Natural Resources Company (the "Company") entered
into a fifth supplemental  indenture (the "Fifth  Supplemental  Indenture") with
Wachovia Bank, National Association as trustee (the "Trustee") which amended the
indenture,  dated as of March 10, 2004,  between the Company and the Trustee (as
amended and supplemented,  the "Indenture") pursuant to which the Company issued
its 5.875% Senior Notes due 2012. The Fifth Supplemental Indenture,  among other
things,  permanently  removed  substantially  all of the operating  restrictions
contained in the Indenture.

The Fifth  Supplemental  Indenture is attached as Exhibit 4.1, and the terms and
conditions thereof are incorporated herein by reference.


Item 9.01. Financial Statements and Exhibits

     (c)   Exhibits

           4.1  -  Fifth Supplemental Indenture, dated as of September 16, 2005,
                   among the Company,  Pioneer Natural Resources  USA, Inc.,  as
                   Guarantor,   and  Wachovia  Bank,  National  Association,  as
                   Trustee,  with  respect to  that Indenture, dated as of March
                   10, 2004,  between the  Company and  Wachovia Bank,  National
                   Association, as Trustee.






                                   SIGNATURE

     Pursuant to the  requirements  of the Securities  Exchange Act of 1934, the
registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned hereunto duly authorized.



                                     PIONEER NATURAL RESOURCES COMPANY


                                        /s/ Darin G. Holderness
                                     -------------------------------------------
                                     Darin G. Holderness
                                     Vice President and Chief Accounting Officer


Date: September 21, 2005



















                                  EXHIBIT INDEX



         Exhibit
         Number                        Exhibit Title
         -------                       -------------


         4.1(a)         Fifth Supplemental Indenture,  dated as of September 16,
                        2005, among the Company,  Pioneer Natural Resources USA,
                        Inc.,  as  Guarantor,   and  Wachovia   Bank,   National
                        Association, as Trustee, with respect to that Indenture,
                        dated as of  March 10,  2004,  between the  Company  and
                        Wachovia Bank, National Association, as Trustee.

--------------
(a) filed herewith.