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


                                    FORM 10-Q


 / x /           Quarterly Report Pursuant to Section 13 or 15(d)
                     of the Securities Exchange Act of 1934

                For the quarterly period ended September 30, 1997

                                       or

 /   /          Transition Report Pursuant to Section 13 or 15(d)
                     of the Securities Exchange Act of 1934
                For the transition period from _______ to _______


                         Commission File No. 33-26097-08


                        PARKER & PARSLEY 90-B CONV., L.P.
             (Exact name of Registrant as specified in its charter)


                Delaware                                     75-2329284
    (State or other jurisdiction of                       (I.R.S. Employer
     incorporation or organization)                    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)

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the  preceding 12 months (or for such  shorter  period that the  Registrant  was
required  to file  such  reports),  and  (2) has  been  subject  to such  filing
requirements for the past 90 days.


                                Yes / x / No / /

                               Page 1 of 11 pages.
                            Exhibit index on page 10.


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                        PARKER & PARSLEY 90-B CONV., L.P.

                                TABLE OF CONTENTS


                                                                       Page
                          Part I. Financial Information

Item 1.    Financial Statements

           Balance Sheets as of September 30, 1997 and
              December 31, 1996   ...................................    3

           Statements of Operations for the three and nine
             months ended September 30,1997 and 1996.................    4

           Statement of Partners' Capital for the nine months
             ended September 30, 1997................................    5

           Statements of Cash Flows for the nine months ended
             September 30,1997 and 1996..............................    6

           Notes to Financial Statements.............................    7

Item 2.    Management's Discussion and Analysis of Financial
             Condition and Results of Operations.....................    7


                      Part II. Other Information

Item 6.    Exhibits and Reports on Form 8-K..........................   10

           27.   Financial Data Schedule

           Signatures................................................   11



                                        2

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                        PARKER & PARSLEY 90-B CONV., L.P.
                        (A Delaware Limited Partnership)

                          Part I. Financial Information

Item 1.   Financial Statements

                                 BALANCE SHEETS

                                                   September 30,   December 31,
                                                       1997            1996
                                                   ------------    -----------
                                                   (Unaudited)
                 ASSETS

Current assets:
  Cash and cash equivalents, including interest
    bearing deposits of $103,298 at September
    30 and $121,219 at December 31                 $    103,585    $   123,797
  Accounts receivable - oil and gas sales               114,154        205,562
                                                    -----------     ----------
           Total current assets                         217,739        329,359
                                                    -----------     ----------
Oil and gas properties - at cost,  based on the
  successful efforts accounting method                9,579,066      9,563,173
Accumulated depletion                                (6,668,922)    (6,489,600)
                                                    -----------     ----------
           Net oil and gas properties                 2,910,144      3,073,573
                                                    -----------     ----------
                                                   $  3,127,883    $ 3,402,932
                                                    ===========     ==========

LIABILITIES AND PARTNERS' CAPITAL

Current liabilities:
  Accounts payable - affiliate                     $     43,740    $    25,296

Partners' capital:
  Managing general partner                               30,841         33,776
  Limited partners (11,897 interests)                 3,053,302      3,343,860
                                                    -----------     ----------
                                                      3,084,143      3,377,636
                                                    -----------     ----------
                                                   $  3,127,883    $ 3,402,932
                                                    ===========     ==========

The financial information included as of September 30, 1997 has been prepared by
           management without audit by independent public accountants.

   The accompanying notes are an integral part of these financial statements.

                                        3

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                        PARKER & PARSLEY 90-B CONV., L.P.
                        (A Delaware Limited Partnership)

                            STATEMENTS OF OPERATIONS
                                   (Unaudited)




                                   Three months ended      Nine months ended
                                      September 30,           September 30,
                                 ---------------------   ---------------------
                                    1997        1996        1997        1996
                                 ---------   ---------   ---------   ---------
Revenues:
  Oil and gas                    $ 242,483   $ 315,670   $ 831,064   $ 951,839
  Interest                           2,014       2,158       6,636       5,315
  Gain on disposition of assets        -           200         -         2,186
                                  --------    --------    --------    --------
                                   244,497     318,028     837,700     959,340
                                  --------    --------    --------    --------
Costs and expenses:
  Oil and gas production           148,353     126,020     406,338     388,934
  General and administrative         8,177      10,073      26,996      30,284
  Depletion                         56,381      60,875     179,322     194,017
                                  --------    --------    --------    --------
                                   212,911     196,968     612,656     613,235
                                  --------    --------    --------    --------
Net income                       $  31,586   $ 121,060   $ 225,044   $ 346,105
                                  ========    ========    ========    ========
Allocation of net income:
  Managing general partner       $     315   $   1,211   $   2,250   $   3,461
                                  ========    ========    ========    ========
  Limited partners               $  31,271   $ 119,849   $ 222,794   $ 342,644
                                  ========    ========    ========    ========
Net income per limited
  partnership interest           $    2.63   $   10.07   $   18.73   $   28.80
                                  ========    ========    ========    ========
Distributions per limited
  partnership interest           $    9.38   $   14.45   $   43.15   $   39.22
                                  ========    ========    ========    ========


         The financial information included herein has been prepared by
           management without audit by independent public accountants.

   The accompanying notes are an integral part of these financial statements.

                                        4

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                        PARKER & PARSLEY 90-B CONV., L.P.
                        (A Delaware Limited Partnership)

                         STATEMENT OF PARTNERS' CAPITAL
                                   (Unaudited)




                                    Managing
                                    general       Limited
                                    partner       partners        Total
                                    --------     ----------     ----------

Balance at January 1, 1997          $ 33,776     $3,343,860     $3,377,636

    Distributions                     (5,185)      (513,352)      (518,537)

    Net income                         2,250        222,794        225,044
                                     -------      ---------      ---------

Balance at September 30, 1997       $ 30,841     $3,053,302     $3,084,143
                                     =======      =========      =========


         The financial information included herein has been prepared by
           management without audit by independent public accountants.

   The accompanying notes are an integral part of these financial statements.

                                        5

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                        PARKER & PARSLEY 90-B CONV., L.P.
                        (A Delaware Limited Partnership)

                            STATEMENTS OF CASH FLOWS
                                   (Unaudited)


                                                           Nine months ended
                                                              September 30,
                                                       ------------------------
                                                          1997           1996
                                                       ----------    ----------
Cash flows from operating activities:
   Net income                                          $  225,044    $  346,105
   Adjustments to reconcile net income to net
      cash provided by operating activities:
        Depletion                                         179,322       194,017
        Gain on disposition of assets                         -          (2,186)
   Changes in assets and liabilities:
        (Increase) decrease in accounts receivable         91,408       (12,316)
        Increase (decrease) in accounts payable            18,444       (13,384)
                                                        ---------     ---------
          Net cash provided by operating activities       514,218       512,236
                                                        ---------     ---------
Cash flows from investing activities:
   Additions to oil and gas properties                    (15,893)       (5,086)
   Proceeds from disposition of assets                        -           2,930
                                                        ---------     ---------
          Net cash used in investing activities           (15,893)       (2,156)
                                                        ---------     ---------
Cash flows from financing activities:
   Cash distributions to partners                        (518,537)     (471,278)
                                                        ---------     ---------
Net increase (decrease) in cash and cash equivalents      (20,212)       38,802
Cash and cash equivalents at beginning of period          123,797       104,953
                                                        ---------     ---------
Cash and cash equivalents at end of period             $  103,585    $  143,755
                                                        =========     =========


         The financial information included herein has been prepared by
           management without audit by independent public accountants.

   The accompanying notes are an integral part of these financial statements.

                                        6

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                        PARKER & PARSLEY 90-B CONV., L.P.
                        (A Delaware Limited Partnership)

                          NOTES TO FINANCIAL STATEMENTS
                               September 30, 1997
                                   (Unaudited)


Note 1.     Basis of presentation

In the opinion of  management,  the unaudited  financial  statements of Parker &
Parsley 90-B Conv.,  L.P. (the  "Partnership")  as of September 30, 1997 and for
the  three  and nine  months  ended  September  30,  1997 and 1996  include  all
adjustments and accruals consisting only of normal recurring accrual adjustments
which are  necessary  for a fair  presentation  of the  results  for the interim
period.  These interim results are not  necessarily  indicative of results for a
full year.  Certain  reclassifications  have been made to prior period financial
statements to conform to the 1997 financial presentations.

Certain  information  and  footnote  disclosure  normally  included in financial
statements prepared in accordance with generally accepted accounting  principles
have been  condensed  or omitted in this Form 10-Q  pursuant  to the results and
regulations of the Securities and Exchange Commission.  The financial statements
should  be read in  conjunction  with the  financial  statements  and the  notes
thereto  contained in the  Partnership's  Report on Form 10-K for the year ended
December 31, 1996, as filed with the Securities and Exchange Commission,  a copy
of which is available upon request by writing to Rich Dealy,  Vice President and
Controller, 303 West Wall, Suite 101, Midland, Texas 79701.

Item 2.     Management's Discussion and Analysis of Financial Condition
              and Results of Operations (1)

As of August 8, 1997, Pioneer Natural Resources USA, Inc. ("Pioneer USA") became
the  general  partner  of  the  Partnership.   Prior  to  August  8,  1997,  the
Partnership's general partner was Parker & Parsley Development L.P. ("PPDLP"), a
wholly-owned  subsidiary  of  Parker &  Parsley  Petroleum  Company  ("Parker  &
Parsley").  On  August  7,  1997,  Parker  &  Parsley  and  Mesa  Inc.  received
shareholder  approval  to merge and create  Pioneer  Natural  Resources  Company
("Pioneer").  On August 8, 1997,  PPDLP was merged with and into  Pioneer USA, a
wholly-owned  subsidiary  of  Pioneer,  resulting  in Pioneer USA  becoming  the
general  partner of the Partnership as PPDLP's  successor by merger.  For a more
complete description of the Parker & Parsley and Mesa Inc. merger, see Pioneer's
Registration  Statement  on Form S-4 as filed  with the  Securities and Exchange
Commission.

Results of Operations

Nine months ended September 30, 1997 compared with nine months ended
   September 30, 1996

Revenues:

The Partnership's  oil and gas revenues  decreased 13% to $831,064 from $951,839
for the nine  months  ended  September  30,  1997 as compared to the nine months
ended  September 30,  1996.  The decrease in  revenues resulted from declines in

                                        7

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barrels of oil and mcf of gas  produced  and sold and a decrease  in the average
price  received  per barrel of oil,  offset by an increase in the average  price
received per mcf of gas. For the nine months ended  September  30, 1997,  31,575
barrels  of oil were sold  compared  to 35,167  for the same  period in 1996,  a
decrease of 3,592 barrels, or 10%. For the nine months ended September 30, 1997,
89,474 mcf of gas were sold  compared to 99,322 mcf for the same period in 1996,
a decrease of 9,848 mcf, or 10%. The decreases in production volumes were due to
the  decline  characteristics  of the  Partnership's  oil  and  gas  properties.
Management  expects a certain amount of decline in production to continue in the
future  until the  Partnership's  economically  recoverable  reserves  are fully
depleted.

The average price received per barrel of oil decreased $1.05, or 5%, from $20.81
for the nine months  ended  September  30, 1996 to $19.76 for the same period in
1997,  while the average price  received per mcf of gas increased from $2.22 for
the nine months ended  September  30, 1996 to $2.32 for the same period in 1997.
The market price for oil and gas has been extremely volatile in the past decade,
and  management  expects  a certain  amount of  volatility  to  continue  in the
foreseeable  future.  The  Partnership may therefore sell its future oil and gas
production at average prices lower or higher than that received  during the nine
months ended September 30, 1997.

Gain on  disposition of assets of $2,186  received  during the nine months ended
September  30,  1996 was  attributable  to credits  received  of $2,930 from the
disposal of oil and gas  equipment on one well that was plugged and abandoned in
a prior year,  offset by a loss on an abandoned  property of $744 resulting from
the  write-off of remaining  capitalized  well costs on one  saltwater  disposal
well.

Costs and Expenses:

Total  costs and  expenses  decreased  to  $612,656  for the nine  months  ended
September  30,  1997 as compared  to  $613,235  for the same  period in 1996,  a
decrease of $579.  The decrease was due to declines in depletion and general and
administrative expenses ("G&A"), offset by increases in production costs.

Production  costs were $406,338 for the nine months ended September 30, 1997 and
$388,934 for the same period in 1996,  resulting in a $17,404  increase,  or 4%.
The  increase  was the result of higher  well  maintenance  and  workover  costs
incurred in an effort to stimulate well production.

G&A's  components are independent  accounting and engineering  fees and managing
general  partner  personnel  and  operating  costs.   During  this  period,  G&A
decreased,  in aggregate,  11% from $30,284 for the nine months ended  September
30, 1996 to $26,996 for the same period in 1997.

Depletion was $179,322 for the nine months ended  September 30, 1997 compared to
$194,017 for the same period in 1996, representing a decrease of $14,695, or 8%.

Three months ended September 30, 1997 compared with three months ended September
   30, 1996

Revenues:

The Partnership's  oil and gas revenues  decreased 23% to $242,483 from $315,670
for the three  months ended  September  30, 1997 as compared to the three months
ended  September 30, 1996.  The decrease in revenues  resulted from a decline in
the average price received per barrel of oil and declines in barrels  of oil and

                                        8

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mcf of gas produced and sold.  For the three  months ended  September  30, 1997,
9,805 barrels of oil were sold compared to 11,348 for the same period in 1996, a
decrease of 1,543  barrels,  or 14%. For the three months  ended  September  30,
1997,  30,045 mcf of gas were sold  compared  to 34,546  for the same  period in
1996,  a decrease of 4,501 mcf, or 13%.  The  decreases  were due to the decline
characteristics of the Partnership's oil and gas properties.

The average  price  received per barrel of oil  decreased  $3.20,  or 15%,  from
$21.52  during the three months ended  September 30, 1996 to $18.32 for the same
period in 1997,  while the average price  received per mcf of gas increased from
$2.07  during the three months  ended  September  30, 1996 to $2.09 for the same
period in 1997.

Gain on  disposition of assets of $200,  received  during the three months ended
September 30, 1996, was  attributable  to credits  received from the disposal of
oil and gas  equipment  on one well that was  plugged and  abandoned  in a prior
year.

Costs and Expenses:

Total costs and  expenses  increased  to  $212,911  for the three  months  ended
September  30,  1997 as compared  to  $196,968  for the same period in 1996,  an
increase of $15,943,  or 8%. This increase was due to higher  production  costs,
offset by decreases in depletion & G&A.

Production costs were $148,353 for the three months ended September 30, 1997 and
$126,020 for the same period in 1996,  resulting in a $22,333 increase,  or 18%.
The  increase  was the  result of higher  workover  and well  maintenance  costs
incurred in an effort to stimulate well production.

G&A's  components are independent  accounting and engineering  fees and managing
general  partner  personnel  and  operating  costs.   During  this  period,  G&A
decreased, in aggregate,  19%, from $10,073 for the three months ended September
30, 1996 to $8,177 for the same period in 1997.

Depletion was $56,381 for the three months ended  September 30, 1997 compared to
$60,875 for the same period in 1996,  representing a decrease of $4,494,  or 7%,
primarily  attributable to a decline in oil production of 1,543 barrels,  offset
by a decrease  in oil and gas  reserves  during  the third  quarter of 1997 as a
result of lower commodity prices.

Liquidity and Capital Resources

Net Cash Provided by Operating Activities

Net cash  provided by  operating  activities  increased  $1,982  during the nine
months ended  September 30, 1997 from the same period ended  September 30, 1996.
This  increase  was due to a decrease  in  production  costs  paid,  offset by a
decrease in oil and gas sales receipts.

Net Cash Used in Investing Activities

The  Partnership's  investing  activities during the nine months ended September
30, 1997 and 1996  included  expenditures  related to equipment  replacement  on
various oil and gas properties.

Proceeds of $2,930 were received during the nine months ended September 30, 1996
from the sale of oil and gas equipment on one well abandoned in a prior year.

                                        9

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Net Cash Used in Financing Activities

Cash was  sufficient  for the nine  months  ended  September  30,  1996 to cover
distributions to the partners of $518,537 of which $5,185 was distributed to the
managing  general  partner and  $513,352 to the limited  partners.  For the same
period ended  September 30, 1996, cash was sufficient for  distributions  to the
partners of $471,278 of which $4,713 was  distributed  to the  managing  general
partner and $466,565 to the limited partners.

It is expected  that future net cash  provided by operating  activities  will be
sufficient for any capital expenditures and any distributions. As the production
from the properties declines, distributions are also expected to decrease.

---------------

(1)    "Item 2. Management's  Discussion and Analysis of Financial Condition and
       Results of Operations"  contains forward looking  statements that involve
       risks and uncertainties. Accordingly, no assurances can be given that the
       actual  events and  results  will not be  materially  different  than the
       anticipated results described in the forward looking statements.


                           Part II. Other Information

Item 6.     Exhibits and Reports on Form 8-K

(a)   Exhibits

      27.   Financial Data Schedule

(b)   Reports on Form 8-K - none


                                       10

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                        PARKER & PARSLEY 90-B CONV., L.P.
                        (A Delaware Limited Partnership)



                               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 thereunto duly authorized.


                                           PARKER & PARSLEY 90-B CONV., L.P.

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




Dated:  November 10, 1997           By:    /s/ Rich Dealy
                                           ---------------------------------
                                           Rich Dealy, Vice President and
                                             Controller



                                       11

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