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 March 31, 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 / /






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

           Statements of Operations for the three months
             ended March 31, 1999 and 1998.............................    4

           Statement of Partners' Capital for the three months
             ended March 31, 1999......................................    5

           Statements of Cash Flows for the three months
             ended March 31, 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............................   11

           27.1    Financial Data Schedule

           Signatures..................................................   12


                                        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

                                                     March 31,      December 31,
                                                       1999            1998
                                                    -----------     -----------
                                                    (Unaudited)
                 ASSETS

Current assets:
  Cash                                              $    62,501     $    76,330
  Accounts receivable - oil and gas sales               100,431          83,807
                                                     ----------      ----------
        Total current assets                            162,932         160,137
                                                     ----------      ----------
Oil and gas properties - at cost,  based on the
  successful efforts accounting method                9,604,752       9,600,469
Accumulated depletion                                (7,764,741)     (7,703,198)
                                                     ----------      ----------
        Net oil and gas properties                    1,840,011       1,897,271
                                                     ----------      ----------
                                                    $ 2,002,943     $ 2,057,408
                                                     ==========      ==========
LIABILITIES AND PARTNERS' CAPITAL

Current liabilities:
  Accounts payable - affiliate                      $    28,147     $    22,740

Partners' capital:
  Managing general partner                               19,748          20,346
  Limited partners (11,897 interests)                 1,955,048       2,014,322
                                                     ----------      ----------
                                                      1,974,796       2,034,668
                                                     ----------      ----------
                                                    $ 2,002,943     $ 2,057,408
                                                     ==========      ==========



  The financial information included as of March 31, 1999 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
                                                              March 31,
                                                      -------------------------
                                                         1999           1998
                                                      ----------     ----------
Revenues:
  Oil and gas                                         $  153,407     $  207,043
  Interest                                                   939          1,917
  Gain on disposition of assets                              -              123
                                                       ---------      ---------
                                                         154,346        209,083
                                                       ---------      ---------
Costs and expenses:
  Oil and gas production                                 121,603        139,603
  General and administrative                               5,818          6,995
  Depletion                                               61,543         52,780
                                                       ---------      ---------
                                                         188,964        199,378
                                                       ---------      ---------
Net income (loss)                                     $  (34,618)    $    9,705
                                                       =========      =========
Allocation of net income (loss):
  Managing general partner                            $     (346)    $       97
                                                       =========      =========
  Limited partners                                    $  (34,272)    $    9,608
                                                       =========      =========
Net income (loss) per limited partnership interest    $    (2.88)    $      .81
                                                       =========      =========
Distributions per limited partnership interest        $     2.10     $     9.93
                                                       =========      =========




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

     Distributions                         (252)       (25,002)       (25,254)

     Net loss                              (346)       (34,272)       (34,618)
                                      ---------      ---------      ---------

Balance at March 31, 1999            $   19,748     $1,955,048     $1,974,796
                                      =========      =========      =========








         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)




                                                        Three months ended
                                                              March 31,
                                                     -------------------------
                                                        1999            1998
                                                     ----------     ----------
Cash flows from operating activities:
   Net income (loss)                                 $  (34,618)    $    9,705
   Adjustments to reconcile net income (loss) to
     net cash provided by operating activities:
       Depletion                                         61,543         52,780
       Gain on disposition of assets                        -             (123)
   Changes in assets and liabilities:
       Accounts receivable                              (16,624)        33,087
       Accounts payable                                   5,407           (694)
                                                      ---------      ---------
         Net cash provided by operating activities       15,708         94,755
                                                      ---------      ---------
Cash flows from investing activities:
   Additions to oil and gas properties                   (4,283)        (5,025)
   Proceeds from asset dispositions                         -              123
                                                      ---------      ---------
         Net cash used in investing activities           (4,283)        (4,902)
                                                      ---------      ---------
Cash flows used in financing activities:
   Cash distributions to partners                       (25,254)      (119,349)
                                                      ---------      ---------
Net decrease in cash                                    (13,829)       (29,496)
Cash at beginning of period                              76,330        118,712
                                                      ---------      ---------
Cash at end of period                                $   62,501     $   89,216
                                                      =========      =========




         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
                                 March 31, 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 March 31, 1999 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 rules 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

Revenues:

The Partnership's  oil and gas revenues  decreased 26% to $153,407 from $207,043
for the three months ended March 31, 1999 and 1998,  respectively.  The decrease
in  revenues  resulted  from lower  average  prices  received  and  declines  in
production.  For the three months ended March 31,  1999,  9,432  barrels of oil,
3,774  barrels of natural gas liquids  ("NGLs") and 17,569 mcf of gas were sold,
or 16,134 barrel of oil equivalents  ("BOEs").  For the three months ended March
31, 1998,  10,469  barrels of oil,  3,681  barrels of NGLs and 18,363 mcf of gas
were sold, or 17,211 BOEs.

                                        7

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The average  price  received per barrel of oil  decreased  $2.98,  or 20%,  from
$14.74 for the three  months  ended March 31, 1998 to $11.76 for the same period
in 1999. The average price received per barrel of NGLs decreased  $1.45, or 21%,
from 6.85 for the three months ended March 31, 1998 to $5.40 for the same period
in 1999.  The average  price  received per mcf of gas  decreased  16% from $1.50
during the three  months  ended  March 31,  1998 to $1.26 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 three
months ended March 31, 1999.

A continuation of the oil price environment experienced during the first quarter
of 1999 will have an adverse effect 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 three months
ended March 31, 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 $188,964 for the three months ended March
31,  1999 as compared  to  $199,378  for the same period in 1998,  a decrease of
$10,414, or 5%. The decrease was due to declines in production costs and general
and administrative expenses ("G&A"), offset by an increase in depletion.

Production  costs were  $121,603  for the three  months ended March 31, 1999 and
$139,603 for the same period in 1998, resulting in an $18,000 decrease,  or 13%.
The decrease was due to declines in well maintenance costs, production taxes and
workover expenses.

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,  17% from $6,995 for the three months ended March 31,
1998 to $5,818 for the same period in 1999.

Depletion  was $61,543  for the three  months  ended March 31, 1999  compared to
$52,780 for the same period in 1998.  This  represented an increase in depletion
of $8,763,  or 17%. The increase was primarily  the result of a  combination  of
factors that included a decline in proved reserves during the three months ended
March 31, 1999 due to the lower commodity  prices,  offset by 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 and a reduction in oil production
of 1,037 barrels for the period ended March 31, 1999 compared to the same period
in 1998.

                                        8

<PAGE>



Liquidity and Capital Resources

Net Cash Provided by Operating Activities

Net cash provided by operating  activities  decreased  $79,047  during the three
months  ended  March 31, 1999 from the same period in 1998.  This  decrease  was
primarily from a decline in oil and gas sales  receipts,  offset by a decline in
production costs paid.

Net Cash Used in Investing Activities

The  Partnership's  principal  investing  activities  for the three months ended
March 31, 1999 and 1998 were related to  expenditures  for oil and gas equipment
on active properties.

Proceeds from asset dispositions of $123 were recognized during the three months
ended March 31, 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  three  months  ended  March  31,  1999 to  cover
distributions  to the partners of $25,254 of which $252 was  distributed  to the
managing  general  partner  and $25,002 to the  limited  partners.  For the same
period  ended March 31,  1998,  cash was  sufficient  for  distributions  to the
partners of $119,349 of which $1,193 was  distributed  to the  managing  general
partner and $118,156 to the limited partners.

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  early
indications that the nations have initiated their planned  reductions,  have had
some  stabilizing  effect on commodity prices during the later part of the first
quarter of 1999 and into April 1999.  However,  no assurances  can be given that
the  stabilizing  effect of these actions,  or the planned  reductions in export
volumes,  will be sustained for an extended period of time. As a result,  future
commodity prices will have a direct impact on the amount of future distributions
and could result in limited or no distributions to the partners.

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.

                                        9

<PAGE>


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 March 31, 1999, the managing general partner estimates that the assessment
phase is approximately 99% complete and has included, but is not limited to, the
following procedures:

o      the identification of  necessary remediation,  upgrade 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  expects to complete the assessment  phase of its
Year 2000 project by the end of the second  quarter of 1999.  Through  March 31,
1999, the managing general partner had distributed  Year 2000 problem  inquiries
to over 500  entities and has received  responses  to  approximately  48% of the
inquiries.

The remedial  phase of the managing  general  partner's  Year 2000 project is in
varying  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 March 31, 1999, the managing general partner
estimates that the remedial phase is approximately 79% complete,  on a worldwide
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 is expected
to be completed by mid-1999.  The managing general  partner's Year 2000 remedial
actions have not delayed other information technology projects or upgrades.

                                       10

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

The managing  general  partner  expects that its total costs related to the Year
2000 problem will approximate $3.6 million, of which approximately $500 thousand
will have been incurred to replace non-compliant information technology systems.
As of March 31, 1999, the managing general partner's total costs incurred on the
Year 2000 problem were $2.4 million,  of which  approximately $200 thousand were
incurred to replace non-compliant systems.

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.

In the  assessment  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.


                                       11

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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:  May 11, 1999              By:      /s/ Rich Dealy 
                                           ---------------------------------
                                           Rich Dealy, Vice President
                                             and Chief Accounting Officer



                                       12

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