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


                                    FORM 10-Q


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


                For the quarterly period ended September 30, 1999


                         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>



                        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, 1999 and
              December 31, 1998....................................    3

           Statements of Operations for the three and nine
             months ended September 30, 1999 and 1998..............    4

           Statement of Partners' Capital for the nine months
             ended September 30, 1999..............................    5

           Statements of Cash Flows for the nine months ended
             September 30, 1999 and 1998...........................    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........................   12

           27.1   Financial Data Schedule

           Signatures..............................................   13



                                        2

<PAGE>



                        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,
                                                       1999            1998
                                                  ------------     -----------
                                                  (Unaudited)
                 ASSETS

Current assets:
  Cash                                            $   117,867      $    76,330
  Accounts receivable - oil and gas sales             145,091           83,807
                                                   ----------       ----------
           Total current assets                       262,958          160,137
                                                   ----------       ----------
Oil and gas properties - at cost,  based on the
  successful efforts accounting method              9,609,886        9,600,469
Accumulated depletion                              (7,821,817)      (7,703,198)
                                                   ----------       ----------
           Net oil and gas properties               1,788,069        1,897,271
                                                   ----------       ----------
                                                  $ 2,051,027      $ 2,057,408
                                                   ==========       ==========
LIABILITIES AND PARTNERS' CAPITAL

Current liabilities:
  Accounts payable - affiliate                    $    37,289      $    22,740

Partners' capital:
  Managing general partner                             20,137           20,346
  Limited partners (11,897 interests)               1,993,601        2,014,322
                                                   ----------       ----------
                                                    2,013,738        2,034,668
                                                   ----------       ----------
                                                  $ 2,051,027      $ 2,057,408
                                                   ==========       ==========




The financial information included as of September 30, 1999 has been prepared by
          management without audit by independent public accountants.

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

                                        3

<PAGE>



                        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,
                                  ---------------------   ---------------------
                                     1999        1998        1999        1998
                                  ---------   ---------   ---------   ---------
Revenues:
  Oil and gas                     $ 255,759   $ 184,754   $ 605,410   $ 595,195
  Interest                            1,627       1,624       3,526       5,099
  Gain on disposition of assets         -           -           -           123
                                   --------    --------    --------    --------
                                    257,386     186,378     608,936     600,417
                                   --------    --------    --------    --------
Costs and expenses:
  Oil and gas production            115,396     125,327     352,051     399,471
  General and administrative         10,343       5,428      22,588      19,129
  Depletion                          27,690      66,731     118,619     180,935
                                   --------    --------    --------    --------
                                    153,429     197,486     493,258     599,535
                                   --------    --------    --------    --------
Net income (loss)                 $ 103,957   $ (11,108)  $ 115,678   $     882
                                   ========    ========    ========    ========
Allocation of net income (loss):
  Managing general partner        $   1,040   $    (111)  $   1,157   $       9
                                   ========    ========    ========    ========
  Limited partners                $ 102,917   $ (10,997)  $ 114,521   $     873
                                   ========    ========    ========    ========
Net income (loss) per limited
  partnership interest            $    8.65   $    (.93)  $    9.63   $     .07
                                   ========    ========    ========    ========
Distributions per limited
  partnership interest            $    7.47   $    4.30   $   11.37   $   18.99
                                   ========    ========    ========    ========



         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

<PAGE>



                        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, 1999           $   20,346     $2,014,322     $2,034,668

    Distributions                        (1,366)      (135,242)      (136,608)

    Net income                            1,157        114,521        115,678
                                      ---------      ---------      ---------

Balance at September 30, 1999        $   20,137     $1,993,601     $2,013,738
                                      =========      =========      =========






         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

<PAGE>



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

                            STATEMENTS OF CASH FLOWS
                                   (Unaudited)



                                                          Nine months ended
                                                             September 30,
                                                      ------------------------
                                                         1999           1998
                                                      ---------     ----------
Cash flows from operating activities:
   Net income                                         $ 115,678     $      882
   Adjustments to reconcile net income to net
      cash provided by operating activities:
        Depletion                                       118,619        180,935
        Gain on disposition of assets                       -             (123)
   Changes in assets and liabilities:
        Accounts receivable                             (61,284)        26,849
        Accounts payable                                 14,549         16,878
                                                       --------      ---------
          Net cash provided by operating activities     187,562        225,421
                                                       --------      ---------
Cash flows from investing activities:
   Additions to oil and gas properties                   (9,417)       (14,131)
   Proceeds from asset dispositions                         -              123
                                                       --------      ---------
          Net cash used in investing activities          (9,417)       (14,008)
                                                       --------      ---------
Cash flows used in financing activities:
   Cash distributions to partners                      (136,608)      (228,234)
                                                       --------      ---------
Net increase (decrease) in cash                          41,537        (16,821)
Cash at beginning of period                              76,330        118,712
                                                       --------      ---------
Cash at end of period                                 $ 117,867     $  101,891
                                                       ========      =========




         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

<PAGE>



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

                          NOTES TO FINANCIAL STATEMENTS
                               September 30, 1999
                                   (Unaudited)


Note 1.     Organization and nature of operations

Parker & Parsley 90-B Conv., L.P. (the "Partnership") was organized as a general
partnership  in 1990 under the laws of the State of Texas and was converted to a
Delaware limited partnership on August 1, 1991.

The Partnership  engages  primarily in oil and gas development and production in
Texas and is not involved in any industry segment other than oil and gas.

Note 2.     Basis of presentation

In  the  opinion  of  management,  the  unaudited  financial  statements  of the
Partnership  as of  September  30, 1999 and for the three and nine months  ended
September 30, 1999 and 1998 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  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, 1998, as filed with the Securities and Exchange Commission,  a copy
of which is available upon request by writing to Rich Dealy,  Vice President and
Chief Accounting Officer,  5205 North O'Connor  Boulevard,  1400 Williams Square
West, Irving, Texas 75039-3746.

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

Results of Operations

Nine months ended September 30, 1999 compared with nine months ended
   September 30, 1998

Revenues:

The  Partnership's  oil and gas  revenues  increased  slightly to $605,410  from
$595,195 for the nine months ended  September  30, 1999 and 1998,  respectively.
The increase in revenues resulted from higher average prices received, offset by
a decrease in production.  For the nine months ended September 30, 1999,  27,016

                                        7

<PAGE>



barrels of oil, 13,167 barrels of natural gas liquids ("NGLs") and 54,094 mcf of
gas were sold, or 49,199 barrel of oil equivalents ("BOEs"). For the nine months
ended  September 30, 1998,  31,203  barrels of oil,  13,025  barrels of NGLs and
56,560 mcf of gas were sold, or 53,655 BOEs.

The average  price  received per barrel of oil  increased  $1.78,  or 13%,  from
$13.46  for the nine  months  ended  September  30,  1998 to $15.24 for the same
period in 1999. The average price  received per barrel of NGLs increased  $1.45,
or 21%, from $6.88 during the nine months ended  September 30, 1998 to $8.33 for
the same period in 1999.  The average price received per mcf of gas increased 3%
from $1.51 for the nine months  ended  September  30, 1998 to $1.55 for the same
period in 1999. 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, 1999.

The volatility of commodity prices has had, and continues to have, a significant
impact on the Partnership's revenues and operating cash flow and could result in
additional  decreases to the  carrying  value of the  Partnership's  oil and gas
properties.

A gain on disposition  of assets of $123 was  recognized  during the nine months
ended  September 30, 1998 from the sale of equipment on one  saltwater  disposal
well plugged and abandoned in a prior year.

Costs and Expenses:

Total  costs and  expenses  decreased  to  $493,258  for the nine  months  ended
September  30,  1999 as compared  to  $599,535  for the same  period in 1998,  a
decrease of $106,277,  or 18%. The decrease was due to declines in depletion and
production costs,  offset by an increase in general and administrative  expenses
("G&A").

Production  costs were $352,051 for the nine months ended September 30, 1999 and
$399,471 for the same period in 1998,  resulting in a $47,420 decrease,  or 12%.
The decrease was the result of lower well  maintenance  costs,  ad valorem taxes
and production taxes.

G&A's  components are independent  accounting and engineering  fees and managing
general  partner  personnel  and  operating  costs.   During  this  period,  G&A
increased,  in aggregate,  18% from $19,129 for the nine months ended  September
30, 1998 to $22,588 for the same period in 1999.

Depletion was $118,619 for the nine months ended  September 30, 1999 compared to
$180,935  for the same period in 1998,  representing  a decrease of $62,316,  or
34%. This decrease was  primarily due to an increase in proved  reserves  during
the period  ended  September  30,  1999 due to the higher  commodity  prices,  a
reduction in oil production of 4,187 barrels for the nine months ended September
30,  1999  compared  to  the  same  period  in  1998  and  a  reduction  in  the
Partnership's  net  depletable  basis  from  charges  taken in  accordance  with
Statement  of  Financial  Accounting  Standards  No.  121,  "Accounting  for the
Impairment of  Long-Lived  Assets and for  Long-Lived  Assets to be Disposed Of"
("SFAS 121") during the fourth quarter of 1998.

                                        8

<PAGE>




Three months ended September 30, 1999 compared with three months ended September
   30, 1998

Revenues:

The Partnership's  oil and gas revenues  increased 38% to $255,759 from $184,754
for the three  months  ended  September  30,  1999 and 1998,  respectively.  The
increase in revenues  resulted from higher average prices received,  offset by a
decrease in  production.  For the three months ended  September 30, 1999,  8,909
barrels of oil, 4,497 barrels of NGLs and 17,772 mcf of gas were sold, or 16,368
BOEs.  For the three months ended  September  30, 1998,  10,050  barrels of oil,
4,915 barrels of NGLs and 19,838 mcf of gas were sold, or 18,271 BOEs.

The average  price  received per barrel of oil  increased  $6.97,  or 56%,  from
$12.36  during the three months ended  September 30, 1998 to $19.33 for the same
period in 1999. The average price  received per barrel of NGLs increased  $5.01,
or 81%,  from $6.24 during the three months ended  September  30, 1998 to $11.25
for the same period in 1999. The average price received per mcf of gas increased
23% from $1.51 during the three months ended September 30, 1998 to $1.85 for the
same period in 1999.

Costs and Expenses:

Total costs and  expenses  decreased  to  $153,429  for the three  months  ended
September  30,  1999 as compared  to  $197,486  for the same  period in 1998,  a
decrease of $44,057,  or 22%. This decrease was due to declines in depletion and
production costs, offset by an increase in G&A.

Production costs were $115,396 for the three months ended September 30, 1999 and
$125,327 for the same period in 1998, resulting in a $9,931 decrease, or 8%. The
decrease was the result of lower ad valorem  taxes and well  maintenance  costs,
offset by an increase in production taxes.

During  this  period,  G&A  increased  from  $5,428 for the three  months  ended
September  30, 1998 to $10,343 for the same period in 1999.  The increase in G&A
was due to accrued  1999 tax  processing  services  as  compared to the 1998 tax
services which were paid during the first six months of 1999.

Depletion was $27,690 for the three months ended  September 30, 1999 compared to
$66,731 for the same period in 1998, representing a decrease of $39,041, or 59%.
This  decrease  was  primarily  attributable  to an increase in proved  reserves
during the  period  ended  September  30,  1999 as a result of higher  commodity
prices, a decrease in oil production of 1,141 barrels for the three months ended
September  30, 1999  compared to the same period in 1998 and a reduction  in the
Partnership's  net depletable  basis from charges taken in accordance  with SFAS
121 during the fourth quarter of 1998.

Liquidity and Capital Resources

Net Cash Provided by Operating Activities

Net cash  provided by operating  activities  decreased  $37,859  during the nine
months ended  September 30, 1999 from the same period ended  September 30, 1998.
This decrease  was primarily  due to a decline in oil and gas sales  receipts of

                                        9

<PAGE>



$77,918 and a $1,573 decline in interest income,  offset by decreases of $38,335
in production costs paid and $3,297 in G&A expenses paid.

Net Cash Used in Investing Activities

The  Partnership's  investing  activities during the nine months ended September
30, 1999 and 1998  included  expenditures  related to equipment  replacement  on
various oil and gas properties.

Proceeds from asset  dispositions  of $123 were received  during the nine months
ended  September 30, 1998 from the sale of equipment on one  saltwater  disposal
well abandoned in a prior year.

Net Cash Used in Financing Activities

Cash was  sufficient  for the nine  months  ended  September  30,  1999 to cover
distributions to the partners of $136,608 of which $1,366 was distributed to the
managing  general  partner and  $135,242 to the limited  partners.  For the same
period ended  September 30, 1998, cash was sufficient for  distributions  to the
partners of $228,234 of which $2,282 was  distributed  to the  managing  general
partner and $225,952 to the limited partners.

From the third  quarter of 1997 through the first  quarter of 1999,  there was a
declining  trend in oil and gas price levels.  During the first quarter of 1999,
the  Organization of Petroleum  Exporting  Countries and certain other crude oil
exporting  nations announced  reductions in their planned export volumes.  These
announcements,  together  with the  enactment of announced  reductions in export
volumes,  have had a  positive  impact on world  crude oil  prices  since  first
quarter  of 1999.  No  assurances  can be given  that the  reductions  in export
volumes or the positive  trend in oil and gas commodity  prices can be sustained
for an extended period of time.

Year 2000 Project Readiness

Historically,  many computer programs have been developed that use only the last
two digits in a date to refer to a year.  As the year 2000 nears,  the inability
of such  computer  programs and embedded  technologies  to  distinguish  between
"1900" and "2000" has given rise to the "Year 2000" problem. Theoretically, such
computer  programs and related  technology  could fail outright,  or communicate
inaccurate  data,  if not  remediated  or replaced.  With the  proliferation  of
electronic  data  interchange,  the Year 2000 problem  represents a  significant
exposure to the entire  global  community,  the full  extent of which  cannot be
accurately assessed.

In proactive  response to the Year 2000 problem,  the managing  general  partner
established  a "Year  2000"  project to  assess,  to the  extent  possible,  the
Partnership's and the managing general partner's internal Year 2000 problem;  to
take remedial  actions  necessary to minimize the Year 2000 risk exposure to the
managing  general  partner and  significant  third parties with whom it has data
interchange;  and, to test its systems and processes once remedial  actions have
been taken. The managing general partner has contracted with IBM Global Services
to perform the assessment and remedial phases of its Year 2000 project.

As of September 30, 1999, the assessment phase of the managing general partner's
Year 2000  project is  complete  and has  included,  but was not limited to, the
following procedures:

                                       10

<PAGE>



o      the identification of necessary remediation,  upgrades and/or replacement
       of existing information technology applications and systems;

o      the  assessment  of   non-information   technology  exposures,   such  as
       telecommunications  systems,  security  systems,  elevators  and  process
       control equipment;

o      the  initiation  of inquiry and  dialogue  with  significant  third party
       business partners, customers and suppliers in an effort to understand and
       assess their Year 2000  problems,  readiness and potential  impact on the
       managing general partner and its Year 2000 problem;

o      the   implementation  of  processes   designed  to  reduce  the  risk  of
       reintroduction  of Year 2000 problems into the managing general partner's
       systems and business processes; and,

o      the formulation of  contingency  plans for  mission-critical  information
       technology systems.

The managing general partner distributed Year 2000 problem inquiries to over 500
entities and has received responses to approximately 52% of the inquiries.

The remedial phase of the managing general partner's Year 2000 project is in the
final stages of  completion  as it pertains to the  remediation  of  information
technology and non-information technology applications and systems in the United
States,  Canada and  Argentina.  As of September 30, 1999, the remedial phase of
the managing general partner's Year 2000 project was approximately 98% complete,
on a world wide basis,  subject to  continuing  evaluations  of the responses to
third party  inquiries and to the testing phase results.  The remedial phase has
included the upgrade  and/or  replacement  of certain  application  and hardware
systems.  The managing  general  partner has upgraded its Artesia general ledger
accounting  systems through remedial coding and has completed the testing of the
system for Year 2000 compliance.  The remediation of non-information  technology
was 97% complete as of September  30, 1999,  and was  completed in October 1999.
The managing general partner's Year 2000 remedial actions have not delayed other
information technology projects or upgrades.

The testing  phase of the  managing  general  partner's  Year 2000 project is on
schedule.  The managing general partner completed the testing of non-information
technology  remediation in October 1999.  The testing of information  technology
remediation is scheduled to be completed by the end of November 1999.

The managing  general  partner now expects  that its total costs  related to the
Year 2000 problem will approximate  $2.9 million.  As of September 30, 1999, the
managing  general  partner's  total costs incurred on the Year 2000 problem were
$2.5 million.

The risks  associated with the Year 2000 problem are  significant.  A failure to
remedy a critical  Year 2000 problem could have a materially  adverse  affect on
the Partnership's results of operations and financial condition. The most likely
worst case scenario  which may be encountered as a result of a Year 2000 problem
could include  information and non-information  system failures,  the receipt or
transmission of erroneous  data, lost data or a combination of similar  problems
of a magnitude that cannot be accurately assessed at this time.

                                       11

<PAGE>



In the  business  continuity  and  contingency  planning  phase of the  managing
general partner's Year 2000 project, contingency plans were designed to mitigate
the exposures to mission critical  information  technology systems,  such as oil
and gas sales receipts, vendor and royalty cash distributions,  debt compliance,
accounting,  and employee  compensation.  Such contingency  plans anticipate the
extensive utilization of third-party data processing services, personal computer
applications  and the  substitution  of courier  and mail  services  in place of
electronic data interchange.  Given the uncertainties regarding the scope of the
Year 2000 problem and the compliance of significant third parties,  there can be
no  assurance  that  contingency  plans  will  have  anticipated  all Year  2000
scenarios.


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

(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

       27.1   Financial Data Schedule

(b)    Reports on Form 8-K - none


                                       12

<PAGE>


                        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 12, 1999         By:      /s/ Rich Dealy
                                           ---------------------------------
                                           Rich Dealy, Vice President and
                                             Chief Accounting Officer



                                       13

<PAGE>