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): March 31, 1998



                           PARKER & PARSLEY 91-B, L.P.
             (Exact name of Registrant as specified in its charter)




                Delaware                33-38582-02            75-2397335
    (State or other jurisdiction of     Commission          (I.R.S. Employer
     incorporation or organization)     File Number      Identification Number)




303 West Wall, Suite 101, Midland, Texas                          79701
(Address of principal executive offices)                        (Zip code)



       Registrant's Telephone Number, including area code : (915) 683-4768


                                 Not applicable
              (Former name, former address and former fiscal year,
                         if changed since last report)




<PAGE>



                           Parker & Parsley 91-B, L.P.



Item 4.   Changes in Registrant's Certifying Accountants

The general partner of Parker & Parsley 91-B, L.P. (the "Partnership"),  Pioneer
Natural Resources USA, Inc., has approved the engagement of Ernst & Young LLP as
the Partnership's  independent  auditors for the fiscal year ending December 31,
1998.  Ernst & Young LLP will replace the firm of KPMG Peat  Marwick LLP,  which
was dismissed as auditors of the Partnership  after  completing the audit of the
Partnership for the fiscal year ending December 31, 1997.

The reports of KPMG Peat Marwick LLP on the Partnership's  financial  statements
for the past two fiscal years did not contain an adverse opinion or a disclaimer
of opinion and were not qualified or modified as to uncertainty, audit scope, or
accounting principles.

In connection with the audits of the Partnership's financial statements for each
of the two  fiscal  years  ended  December  31,  1997 and  1996,  there  were no
disagreements with KPMG Peat Marwick LLP on any matters of accounting principles
or practices,  financial statement disclosure,  or auditing scope and procedures
which,  if not resolved to the  satisfaction of KPMG Peat Marwick LLP would have
caused KPMG Peat Marwick LLP to make reference to the matter in their report.

The Partnership  requested KPMG Peat Marwick LLP to furnish the Partnership with
a letter  addressed to the Securities and Exchange  Commission  stating  whether
KPMG Peat Marwick LLP agrees with the above statements. A copy of that letter is
included as Exhibit 16.1 to the report on Form 8-K.


                                        2

<PAGE>





                               S I G N A T U R E S


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.

                                       PARKER & PARSLEY 91-B, L.P.

                                       By:  Pioneer Natural Resources USA, Inc.
                                              Managing General Partner



Date:   April 2, 1998             By:     /s/ Rich Dealy
                                       ------------------------------------
                                           Rich Dealy
                                           Vice President and
                                           Chief Accounting Officer



                                        3

<PAGE>



Exhibit Index                                                           Page


    16.1*    Letter from the independent certified public accountants     5




* Filed herewith.





                                        4

<PAGE>


                                                                  Exhibit 16.1


                              KPMG Peat Marwick LLP
                         300 North Marienfeld, Suite 300
                              Midland, Texas 79701




April 1, 1998



Securities and Exchange Commission
Washington, D.C.  20549

Ladies and Gentlemen:

We were  previously  principal  accountants for Parker & Parsley 91-B, L.P. and,
under the  date of March 20,  1998,  we reported on the financial  statements of
Parker & Parsley 91-B,  L.P. as of and for the years ended December 31, 1997 and
1996.  On  March  28,  1998,  our  appointment  as  principal   accountants  was
terminated. We have read Parker & Parsley 91-B, L.P.'s statements included under
Item 4 of its Form 8-K dated March 31, 1998 and we agree with such statements.

                                                Very truly yours,



                                                KPMG Peat Marwick LLP


                                        5

<PAGE>
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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): March 31, 1998

                           PARKER & PARSLEY 91-B, L.P.
             (Exact name of Registrant as specified in its charter)

                Delaware                33-38582-02            75-2397335
    (State or other jurisdiction of     Commission          (I.R.S. Employer
     incorporation or organization)     File Number      Identification Number)

303 West Wall, Suite 101, Midland, Texas                          79701
(Address of principal executive offices)                        (Zip code)

       Registrant's Telephone Number, including area code : (915) 683-4768

                                 Not applicable
              (Former name, former address and former fiscal year,
                         if changed since last report)
Parker & Parsley 91-B, L.P.

Item 4.   Changes in Registrant's Certifying Accountants

The general partner of Parker & Parsley 91-B, L.P. (the "Partnership"),  Pioneer
Natural Resources USA, Inc., has approved the engagement of Ernst & Young LLP as
the Partnership's  independent  auditors for the fiscal year ending December 31,
1998.  Ernst & Young LLP will replace the firm of KPMG Peat  Marwick LLP,  which
was dismissed as auditors of the Partnership  after  completing the audit of the
Partnership for the fiscal year ending December 31, 1997.

The reports of KPMG Peat Marwick LLP on the Partnership's  financial  statements
for the past two fiscal years did not contain an adverse opinion or a disclaimer
of opinion and were not qualified or modified as to uncertainty, audit scope, or
accounting principles.

In connection with the audits of the Partnership's financial statements for each
of the two  fiscal  years  ended  December  31,  1997 and  1996,  there  were no
disagreements with KPMG Peat Marwick LLP on any matters of accounting principles
or practices,  financial statement disclosure,  or auditing scope and procedures
which,  if not resolved to the  satisfaction of KPMG Peat Marwick LLP would have
caused KPMG Peat Marwick LLP to make reference to the matter in their report.

The Partnership  requested KPMG Peat Marwick LLP to furnish the Partnership with
a letter  addressed to the Securities and Exchange  Commission  stating  whether
KPMG Peat Marwick LLP agrees with the above statements. A copy of that letter is
included as Exhibit 16.1 to the report on Form 8-K.

                                        2
S I G N A T U R E S

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.

                                       PARKER & PARSLEY 91-B, L.P.

                                       By:  Pioneer Natural Resources USA, Inc.
                                              Managing General Partner

Date:   April 2, 1998             By:     /s/ Rich Dealy
                                       ------------------------------------
                                           Rich Dealy
                                           Vice President and
                                           Chief Accounting Officer

                                        3
Exhibit Index                                                           Page

    16.1*    Letter from the independent certified public accountants     5

* Filed herewith.

                                        4
Exhibit 16.1

                              KPMG Peat Marwick LLP
                         300 North Marienfeld, Suite 300
                              Midland, Texas 79701

April 1, 1998

Securities and Exchange Commission
Washington, D.C.  20549

Ladies and Gentlemen:

We were  previously  principal  accountants for Parker & Parsley 91-B, L.P. and,
under the  date of March 20,  1998,  we reported on the financial  statements of
Parker & Parsley 91-B,  L.P. as of and for the years ended December 31, 1997 and
1996.  On  March  28,  1998,  our  appointment  as  principal   accountants  was
terminated. We have read Parker & Parsley 91-B, L.P.'s statements included under
Item 4 of its Form 8-K dated March 31, 1998 and we agree with such statements.

                                                Very truly yours,

                                                KPMG Peat Marwick LLP

                                        5