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                       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, 1999

[ ]  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
     SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD
     FROM ----------------- TO -----------------

                         COMMISSION FILE NUMBER 1-8432

                              MESA OFFSHORE TRUST
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

                   TEXAS                                  76-6004065
          (STATE OF INCORPORATION                      (I.R.S. EMPLOYER
             OR ORGANIZATION)                         IDENTIFICATION NO.)

           CHASE BANK OF TEXAS,
           NATIONAL ASSOCIATION
         CORPORATE TRUST DIVISION
              712 MAIN STREET
              HOUSTON, TEXAS                                77002
 (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)                 (ZIP CODE)

                                 1-800-852-1422
              (REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE)

     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 [ ]

     Indicate the number of shares outstanding of each of the registrant's
classes of common stock, as of the latest practicable date.

     As of November 12, 1999 -- 71,980,216 Units of Beneficial Interest in Mesa
Offshore Trust.

================================================================================
<PAGE>
                        PART I -- FINANCIAL INFORMATION

ITEM 1.  FINANCIAL STATEMENTS

                              MESA OFFSHORE TRUST

                       STATEMENTS OF DISTRIBUTABLE INCOME
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                         THREE MONTHS ENDED        NINE MONTHS ENDED
                                           SEPTEMBER 30,             SEPTEMBER 30,
                                       ----------------------  --------------------------
                                          1999        1998         1999          1998
                                       ----------  ----------  ------------  ------------
<S>                                    <C>         <C>         <C>           <C>
Royalty income.......................  $  588,131  $  535,215  $  2,876,656  $  1,670,489
Interest income......................      23,872      42,747        72,299        98,328
General and administrative expense...     (41,323)    (74,688)     (419,426)     (281,678)
                                       ----------  ----------  ------------  ------------
     Distributable income............  $  570,680  $  503,274  $  2,529,529  $  1,487,139
                                       ==========  ==========  ============  ============
     Distributable income per unit...  $    .0079  $    .0070  $      .0351  $      .0207
                                       ==========  ==========  ============  ============
</TABLE>

               STATEMENTS OF ASSETS, LIABILITIES AND TRUST CORPUS

                                        SEPTEMBER 30,      DECEMBER 31,
                                             1999              1998
                                       ----------------  ----------------
                                         (UNAUDITED)

               ASSETS
Cash and short-term investments......  $      2,455,079  $      1,836,398
Interest receivable..................            23,872            23,102
Net overriding royalty interest in
  oil and gas properties.............       380,905,000       380,905,000
Accumulated amortization.............      (380,868,692)     (380,848,599)
                                       ----------------  ----------------
                                       $      2,515,259  $      1,915,901
                                       ================  ================
    LIABILITIES AND TRUST CORPUS
Reserve for Trust expenses...........  $      1,908,271  $      1,859,500
Distributions payable................           570,680         --
Trust corpus (71,980,216 units of
  beneficial interest
  authorized and outstanding)........            36,308            56,401
                                       ----------------  ----------------
                                       $      2,515,259  $      1,915,901
                                       ================  ================

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

                                       1
<PAGE>
                              MESA OFFSHORE TRUST

                     STATEMENTS OF CHANGES IN TRUST CORPUS
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                           THREE MONTHS ENDED            NINE MONTHS ENDED
                                             SEPTEMBER 30,                 SEPTEMBER 30,
                                       --------------------------  ------------------------------
                                           1999          1998           1999            1998
                                       ------------  ------------  --------------  --------------
<S>                                    <C>           <C>           <C>             <C>
Trust corpus, beginning of period....  $     39,161  $    118,279  $       56,401  $      248,200
     Distributable income............       570,680       503,274       2,529,529       1,487,139
     Distributions to unitholders....      (570,680)     (503,274)     (2,529,529)     (1,487,139)
     Amortization of net overriding
       royalty interest..............        (2,853)      (61,251)        (20,093)       (191,172)
                                       ------------  ------------  --------------  --------------
Trust corpus, end of period..........  $     36,308  $     57,028  $       36,308  $       57,028
                                       ============  ============  ==============  ==============
</TABLE>

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

                                       2
<PAGE>
                              MESA OFFSHORE TRUST
                         NOTES TO FINANCIAL STATEMENTS
                                  (UNAUDITED)

NOTE 1 -- TRUST ORGANIZATION

     The Mesa Offshore Trust (the "Trust") was created effective December 1,
1982 when Mesa Petroleum Co., predecessor to Mesa Limited Partnership, which was
the predecessor to MESA Inc., transferred a 99.99% interest in the Mesa Offshore
Royalty Partnership (the "Partnership") to the Trust. The Partnership was
created to receive and hold a 90% net overriding royalty interest (the
"Royalty") in ten producing and nonproducing oil and gas properties located in
federal waters offshore Louisiana and Texas (the "Royalty Properties"). Until
August 7, 1997, MESA Inc. owned and operated its assets through Mesa Operating
Co. ("Mesa"), the operator of the Royalty Properties. Mesa Operating Co. is
also the managing general partner of the Partnership (the Managing General
Partners). On August 7, 1997, MESA Inc. merged with and into Pioneer Natural
Resources Company ("Pioneer") formerly a wholly owned subsidiary of MESA, Inc.
and Parker & Parsley Petroleum Company merged with and into Pioneer Natural
Resources USA, Inc. (successor to Mesa Operating Co.), a wholly owned subsidiary
of Pioneer ("PNR") (collectively, the mergers are referred to herein as the
"Merger"). Subsequent to the Merger, Pioneer owns and operates its assets
through PNR and is also the managing general partner of the Partnership. As used
in this report, the term PNR generally refers to the operator of the Royalty
Properties, unless otherwise indicated.

STATUS OF THE TRUST

     The Trust Indenture provides that the Trust will terminate if the total
amount of cash per year received by the Trust falls below certain levels for
each of three successive years (the "Termination Threshold"). The December 31,
1998 reserve report prepared for the Partnership (see the Trust's 1998 Annual
Report on Form 10-K) indicates that Royalty income expected to be received by
the Trust in 2000 could be at or near the Termination Threshold. The reserve
report estimates that future Royalty income to the Trust is approximately $5.2
million (which excludes the $2.1 million of royalty income resulting from the
release of the MMS royalty reserve discussed below) while the Termination
Threshold for 1998 was approximately $1.4 million. It is therefore possible
(depending on the timing of future production and drilling activities, market
conditions, recoupment of unrecovered capital costs and other matters) that in
2000 Royalty income received by the Trust may be below the Termination
Threshold. If Royalty income falls below the Termination Threshold for three
successive years, the Trust would terminate. Upon termination of the Trust, the
Trustee will sell for cash all the assets held in the Trust estate and make a
final distribution to unitholders of any funds remaining after all Trust
liabilities have been satisfied. There are numerous uncertainties inherent in
estimating and projecting the quantity and value of proved reserves for the
Trust properties as many of the Trust properties are nearing the end of their
productive lives and are therefore subject to unforeseen changes in production
rates. As such, there can be no assurance that Royalty income received by the
Trust in 2000 or thereafter will be above the Termination Threshold.

NOTE 2 -- BASIS OF PRESENTATION

     The accompanying unaudited financial information has been prepared by Chase
Bank of Texas, National Association (the "Trustee") in accordance with the
instructions to Form 10-Q, and the Trustee believes such information includes
all the disclosures necessary to make the information presented not misleading.
The information furnished reflects all adjustments which are, in the opinion of
the Trustee, necessary for a fair presentation of the results for the interim
periods presented. The financial information should be read in conjunction with
the financial statements and notes thereto included in the Trust's 1998 Annual
Report on Form 10-K.

                                       3
<PAGE>
     The financial statements of the Trust are prepared on the following basis:

          (a)  Royalty income recorded for a month is the Trust's interest in
     the amount computed and paid by PNR to the Partnership for such month
     rather than either the value of a portion of the oil and gas produced by
     PNR for such month or the amount subsequently determined to be 90% of the
     net proceeds for such month;

          (b)  Interest income, interest receivable and distributions payable to
     unitholders include interest to be earned on short-term investments from
     the financial statement date through the next distribution date;

          (c)  Trust general and administrative expenses are recorded in the
     month they are accrued;

          (d)  Amortization of the net overriding royalty interest, which is
     calculated on the basis of current royalty income in relation to estimated
     future royalty income, is charged directly to trust corpus since such
     amount does not affect distributable income; and

          (e)  Distributions payable are determined on a monthly basis and are
     payable to unitholders of record as of the last business day of each month
     or such any other day as the Trustee determines is required to comply with
     legal or stock exchange requirements. However, cash distributions are made
     quarterly in January, April, July and October, and include interest earned
     from the monthly record dates to the date of distribution.

     This basis for reporting Royalty income is considered to be the most
meaningful because distributions to the unitholders for a month are based on net
cash receipts for such month. However, these statements differ from financial
statements prepared in accordance with generally accepted accounting principles
in several respects. Under such principles, royalty income for a month would be
based on net proceeds from production for such month without regard to when
calculated or received and interest income would include interest earned during
the period covered by the financial statements and would exclude interest from
the period end to the date of distribution.

     The instruments conveying the Royalty provide that PNR will calculate and
pay the Partnership each month an amount equal to 90% of the net proceeds for
the preceding month. Generally, net proceeds means the excess of the amounts
received by PNR from sales of oil and gas from the Royalty Properties plus other
cash receipts over operating and capital costs incurred.

NOTE 3 -- RELEASE OF MMS ROYALTY RESERVE

     During the mid-1980's, PNR withheld approximately $3.5 million ($3.1
million net to the Trust) as a reserve for potential liabilities for royalty
claims made by the Mineral Management Service ("MMS"). The claims by the MMS
included, among other things, disputed transportation allowances attributable to
the Trust's South Marsh Island properties and payments received by PNR from
purchasers as settlements under gas purchase contracts. During 1998, PNR settled
all known claims with the MMS for $3.6 million ($3.2 million net to the Trust)
which significantly reduced the amount in the reserve. The balance of the
reserve, including accrued interest, was approximately $3.4 million ($3.1
million net to the Trust). In May 1999, PNR determined that this reserve was no
longer necessary. Approximately $3.1 million was released to the Trust, subject
to the recovery of an approximate $1.0 million cost carryforward, and included,
net of amounts used to replenish the reserve for Trust expenses, in the second
quarter of 1999 distribution.

                                       4
<PAGE>
ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
        OF OPERATIONS

NOTE REGARDING FORWARD-LOOKING STATEMENTS

     This Form 10-Q includes "forward-looking statements" within the meaning
of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the
Securities Exchange Act of 1934, as amended. All statements other than
statements of historical facts included in this Form 10-Q, including without
limitation the statements under "Management's Discussion and Analysis of
Financial Condition and Results of Operations" and Note 1 to the financial
statements of the Trust regarding the future net revenues of the Trust, are
forward-looking statements. Although Pioneer has advised the Trust that it
believes that the expectations reflected in such forward-looking statements are
reasonable, no assurance can be given that such expectations will prove to have
been correct. Important factors that could cause actual results to differ
materially from expectations ("Cautionary Statements") are disclosed in this
Form 10-Q, including without limitation in conjunction with the forward-looking
statements included in this Form 10-Q and in the Trust's Form 10-K. All
subsequent written and oral forward-looking statements attributable to the Trust
or persons acting on its behalf are expressly qualified in their entirety by the
Cautionary Statements.

STATUS OF POTENTIAL SALE OF TRUST PROPERTIES

     On April 15, 1999, PNR announced the termination of the transaction
contemplated by the April 1, 1999 Purchase and Sales Agreement between PNR and
Costilla Energy, Inc. providing for the sale of certain oil and gas properties
to Costilla. Included with the properties to be sold were PNR's interest in all
of the Royalty properties. PNR has executed a contingency plan to remarket these
properties. If such a sale is consummated, the Trust has been advised that there
should be no significant impact on the Trust, although the precise nature of any
effects cannot be predicted or quantified at this time.

INFORMATION SYSTEMS FOR THE YEAR 2000

     The inability of some computer programs and embedded computer chips to
distinguish between the year 1900 and the year 2000 (the "Year 2000 problem")
poses a serious threat of business disruption to any organization that utilized
computer technology and computer chip technology in their business systems or
equipment. In proactive response to the Year 2000 problem, PNR established a
"Year 2000" project to assess, to the extent possible, PNR's internal Year
2000 problem; to take remedial actions necessary to minimize the Year 2000 risk
exposure to PNR and significant third parties with whom it has data interchange;
and, to test its systems and processes once remedial actions have been taken.
PNR 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 PNR's Year 2000 project
is complete on a worldwide basis and has included, among other procedures, (1)
the identification of necessary remediation, upgrade and/or replacement of
existing information technology applications and systems; (2) the assessment of
non-information technology exposures, such as telecommunications systems,
security systems, elevators and process control equipment; (3) 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 PNR and its Year 2000 problem; (4) the
implementation of processes designed to reduce the risk of reintroduction of
Year 2000 problems into PNR's systems and business processes; and, (5) the
formulation of contingency plans for mission-critical information technology
systems.

     As of September 30, 1999, PNR estimates that the remedial phase is
approximately 98% complete, on a worldwide basis, subject to the continuing
evaluations of the responses from third party inquiries and the testing phase.
The remedial phase has included the upgrade and/or replacement of certain
applications and hardware systems. The remediation of non-information technology
was completed in October 1999. PNR's Year 2000 remedial actions have not delayed
other information technology projects or upgrades. The testing phase of PNR's
Year 2000 project is expected to be completed by the end of November 1999. None
of PNR's costs related to the Year 2000 are passed through to the Trust.

                                       5
<PAGE>
     A failure to remedy a critical Year 2000 problem could have a materially
adverse effect on PNR'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 to PNR that cannot be accurately assessed at this time.

     In the assessment phase of PNR's Year 2000 project, contingency plans were
designed to mitigate the exposure 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.

     The Trustee has developed and is implementing a program to prepare its
systems and applications for the Year 2000, including those used to render
services to the Trust. In that connection, the Trustee intends to have such
systems and applications capable of processing, on and after January 1, 2000
date, and date-related data consistent with the functionality of such systems
and applications, without a material adverse effect upon its performance of
services as Trustee. Third parties that the Trust conducts business with could
be prone to Year 2000 problems that could not be assessed or detected by the
Trust. The Trust is contacting the major third parties to determine whether they
will be able to resolve, in a timely manner, any Year 2000 problems directly
affecting the Trust and to inform them of the Trust's internal assessment of its
Year 2000 review.

     Information above with respect to PNR is based upon information provided by
PNR to the Trustee for use in this Form 10-Q.

FINANCIAL REVIEW

     During the third quarter of 1999, the Trust had distributable income of
$570,680, representing $.0079 per unit, as compared to $503,274, representing
$.0070 per unit in the second quarter of 1998. The per unit amounts of
distributable income for the second quarter of 1999 and 1998 were earned by
month as follows:

                                         1999       1998
                                       ---------  ---------
      July...........................  $  --      $   .0010
      August.........................     --          .0019
      September......................      .0079      .0041
                                       ---------  ---------
                                       $   .0079  $   .0070
                                       =========  =========

     Royalty income increased to $588,131 in the third quarter of 1999 as
compared to $535,215 in the third quarter of 1998. The increase in Royalty
income is primarily due to the increase in natural gas production from West
Delta 61 and 62. See "Operational Review." The Trust will not make any
additional distributions until it has recouped approximately $92,000 of expenses
paid from its reserve for Trust expenses.

     Production volumes for natural gas increased to 392,036 Mcf in the third
quarter of 1999 from 359,001 Mcf in the third quarter of 1998 primarily as a
result of increased production on West Delta 61 and 62 and Brazos A-7 and A-39
partially offset by a decrease in production on South Marsh Island 155 and 156.
The average price received for natural gas was $2.22 per Mcf in the third
quarter of 1999 compared to $2.21 per Mcf in the third quarter of 1998.

     Crude oil, condensate and natural gas liquids production decreased to
10,028 barrels in the third quarter of 1999 from 25,153 barrels in the third
quarter of 1998. The average price received for crude oil, condensate and
natural gas liquids was $16.09 per barrel in the third quarter of 1999, compared
to $12.00 per barrel in the third quarter of 1998.

                                       6
<PAGE>
     The decrease in natural gas and crude oil, condensate and natural gas
liquids production for the nine months ended September 30, 1999 when compared to
the comparable periods of 1998 is primarily attributable to the cessation of
production from the South Marsh Island blocks 155 and 156 in the fourth quarter
of 1998.

     For the nine months ended September 30, 1999, natural gas production
volumes decreased to 854,621 Mcf from 1,164,666 Mcf for the nine months ended
September 30, 1998. Crude oil, condensate and natural gas liquids production
volumes decreased to 18,030 barrels in the first nine months of 1999 as compared
to 49,593 barrels in the first nine months of 1998.

OPERATIONAL REVIEW

     During the mid-1980's, PNR withheld approximately $3.5 million ($3.1
million net to the Trust) as a reserve for potential liabilities for royalty
claims made by the Mineral Management Service ("MMS"). The claims by the MMS
included, among other things, disputed transportation allowances attributable to
the Trust's South Marsh Island properties and payments received by PNR from
purchasers as settlements under gas purchase contracts. During 1998, PNR settled
all known claims with the MMS for $3.6 million ($3.2 million net to the Trust)
which significantly reduced the amount in the reserve. The balance of the
reserve, including accrued interest, was approximately $3.4 million ($3.1
million net to the Trust). In May 1999, PNR determined that this reserve was no
longer necessary. Approximately $3.1 million was released to the Trust, subject
to the recovery of an approximate $1.0 million cost carryforward, and included,
net of amounts used to replenish the reserve for Trust expenses, in the second
quarter of 1999 distribution.

     PNR has advised the Trust that during the third quarter of 1999 its
offshore gas production was marketed under short term contracts at spot market
prices primarily to H&N, Limited. PNR has further advised the Trust that it
expects to continue to market its production under short term contracts for the
foreseeable future. Spot market prices for natural gas in the third quarter of
1999 were lower than spot market prices in the third quarter of 1998.

     The amount of cash distributed by the Trust is dependent on, among other
things, the sales prices and quantities of gas, crude oil, condensate and
natural gas liquids produced from the Royalty Properties and the quantities
sold. Substantial uncertainties exist with regard to future gas and oil prices,
which are subject to fluctuations due to the regional supply and demand for
natural gas and oil, production levels and other activities of OPEC and other
oil and gas producers, weather, industrial growth, conservation measures,
competition and other variables.

     The Brazos A-7 and A-39 block experienced an increase in production due to
new production from a farmout agreement. PNR farmed out a portion of the Brazos
A-7 block to another operator and participated at a 10% working interest in the
completion of an exploratory gas well drilled in the second quarter of 1997.
During the fourth quarter of 1998, PNR incurred $7.35 million ($661,000 net to
the Trust) of completion costs for the Brazos A-7 No. 5 well. As of June 30,
1999, the cost carryforward resulting from the completion costs on the Brazos
A-7 No. 5 well, other capital expenditures and over distributions by PNR were
recovered. The No. 5 well commenced production late in the fourth quarter of
1998 and is currently producing at a rate of approximately 10 MMcf per day.

     The South Marsh Island 155 and 156 blocks experienced a decrease in
production in the third quarter of 1999 as compared to the third quarter of
1998, primarily due to the cessation of production from the A-19 well in late
1998. This block is currently not producing, but a workover was performed in May
1999 to attempt to restore production. The workover was not successful and PNR
is currently exploring several alternatives to attempt to restore production. A
plan should be completed in the fourth quarter of 1999. In 1998, PNR purchased
3-D seismic data for the South Marsh Island 156 block at a cost of $300,000
($189,000 net to the Trust). The data has been evaluated and PNR has no current
plans for additional drilling.

     The West Delta 61 and 62 blocks experienced an increase in oil and in
natural gas production in the third quarter of 1999 as compared to the third
quarter of 1998 primarily due to new production from farmout agreements. In
portions of West Delta block 61, the Trust is receiving Royalty income from this
property pursuant to a farmout agreement with another operator. The interest in
the farmout wells which is

                                       7
<PAGE>
attributable to the Trust, consists of a 7.5% net profits interest. In West
Delta block 62, PNR farmed out portions of the block to another operator,
retaining a 10% (9% net to the Trust) overriding royalty interest. A new well
was drilled in the third quarter of 1998 which encountered 320 net feet of pay
in eight Miocene sands below a true vertical depth of 7,500 feet. In the fourth
quarter of 1998, the operator drilled one development well and one exploratory
well. The development well encountered 250 net feet of pay in seven Miocene
sands. The operator has elected to set a four-pile platform, and production
began in the second quarter of 1999. The exploratory well tested a new fault
block which was determined to be non-commercial. The exploratory well was
subsequently plugged in the first quarter of 1999. The Trust will receive an
11.25% overriding royalty interest in these wells. The Trust began receiving
revenues from these new wells in the third quarter of 1999.

     Matagorda Island 624 oil and natural gas production decreased in the third
quarter of 1999 as compared to the third quarter of 1998, primarily due to
natural production decline. Gross producing rate of the block was approximately
 .85 MMcf of gas and 10 barrels of condensate per day as of September 1999.

TERMINATION OF THE TRUST

     The terms of the Mesa Offshore Trust Indenture provide that the Trust will
terminate upon the first to occur of the following events: (1) the total amount
of cash received per year by the Trust for each of three successive years
commencing after December 31, 1987 is less than 10 times one-third of the total
amount payable to the Trustee as compensation for such three year period or (2)
a vote by the unitholders in favor of termination. Because the Trust will
terminate in the event the total amount of cash received per year by the Trust
falls below certain levels, it would be possible for the Trust to terminate even
though some of the Royalty Properties continued to have remaining productive
lives. For information regarding the estimated remaining life of each of the
Royalty Properties and the estimated future net revenues of the Trust based on
information provided by PNR, see the Trust's 1998 Annual Report on Form 10-K.
Upon termination of the Trust, the Trustee will sell for cash all the assets
held in the Trust estate and make a final distribution to unitholders of any
funds remaining after all Trust liabilities have been satisfied. The discussion
set forth above is qualified in its entirety by reference to the Trust Indenture
itself, which is available upon request from the Trustee. Amounts paid to the
Trustee as compensation were $128,000, $173,000 and $123,000 for the years 1998,
1997, and 1996, respectively.

     The December 31, 1998, reserve report prepared for the Partnership (see the
Trust's 1998 Annual Report on Form 10-K) indicates that 95% of future net
revenues will be received by the Trust during the next four years. As such, it
is possible, depending on the timing of future production, market conditions,
the success of future drilling activities, if any, and other matters, that in
2000 Royalty income received by the Trust may be below the Termination
Threshold. If Royalty income falls below the Termination Threshold for three
successive years, the Trust would terminate pursuant to the terms discussed
above. There are numerous uncertainties inherent in estimating and projecting
the quantity and value of proved reserves for the Trust properties as many of
the Trust properties are nearing the end of their productive lives and are
therefore subject to unforeseen changes in production rates. As such, there can
be no assurance that Royalty income received by the Trust in 2000 will be above
the Termination Threshold.

     The terms of the First Amended and Restated Articles of General Partnership
of the Partnership provide that the Partnership shall dissolve upon the
occurrence of any of the following: (a) December 31, 2030; (b) the election of
the Trustee to dissolve the Partnership; (c) the termination of the Trust; (d)
the bankruptcy of the Managing General Partner; or (e) the dissolution of the
Managing General Partner or its election to dissolve the Partnership; provided
that the Managing General Partner shall not elect to dissolve the Partnership so
long as the Trustee remains the only other partner of the Partnership. In the
event of a dissolution of the Partnership and a subsequent winding up and
termination thereof, the assets of the Partnership (i.e., the Royalty interest)
could either (i) be distributed in kind ratably to the Managing General Partner
and the Trustee or (ii) be sold and the proceeds thereof distributed ratably to
the Managing General Partner and the Trustee. In the event of a sale of the
Royalty and a distribution of the cash proceeds to the Trustee, the Trustee
would make a final distribution to unitholders of such cash proceeds plus any
other

                                       8
<PAGE>
cash held by the Trust after the payment of or provision for all liabilities of
the Trust, and the Trust would be terminated.

     The following tables provide summaries of the calculations of the net
proceeds attributable to the Partnership's royalty interests (unaudited):

<TABLE>
<CAPTION>
                                                     SOUTH
                                        BRAZOS       MARSH        WEST      MATAGORDA
                                        A-7 AND   ISLAND 155    DELTA 61      ISLAND
                                         A-39       AND 156      AND 62        624          TOTAL
                                       ---------  -----------  ----------   ----------   -----------
<S>                                    <C>        <C>          <C>          <C>          <C>
THREE MONTHS ENDED
  SEPTEMBER 30, 1999:
    Ninety percent of gross
      proceeds.......................  $ 321,079  $    11,081  $  623,737    $ 76,797    $ 1,032,694
    Less ninety percent of --
      Operating expenditures.........   (103,601)    (139,267)    (64,680)    (75,293)      (382,841)
      Capital costs recovered........       (205)     (61,458)     --          --            (61,663)
      Accrual for future abandonment
         costs.......................     --          --           --          --            --
                                       ---------  -----------  ----------   ----------   -----------
    Net proceeds (excess costs)......  $ 217,273  $  (189,644) $  559,057    $  1,504    $   588,190
                                       =========  ===========  ==========   ==========   ===========
    Trust share of net proceeds
      (99.99%).......................                                                    $   588,131
                                                                                         ===========
    Production Volumes and Average
      Prices:
      Crude oil, condensate and
         natural gas liquids
         (Bbls)......................        326        1,151       8,191         360         10,028
                                       =========  ===========  ==========   ==========   ===========
      Average sales price per Bbl....  $   14.40  $     14.69  $    16.41    $  14.83    $     16.09
                                       =========  ===========  ==========   ==========   ===========
      Natural gas (Mcf)..............    151,452           70     200,756      39,758        392,036
                                       =========  ===========  ==========   ==========   ===========
      Average sales price per Mcf....  $    2.09  $   --       $     2.44    $   1.80    $      2.22
                                       =========  ===========  ==========   ==========   ===========
    Producing wells..................          4      --                3           1              8
</TABLE>

<TABLE>
<CAPTION>
                                                     SOUTH
                                        BRAZOS       MARSH        WEST      MATAGORDA
                                        A-7 AND   ISLAND 155    DELTA 61      ISLAND
                                         A-39       AND 156      AND 62        624          TOTAL
                                       ---------  -----------  ----------   ----------   -----------
<S>                                    <C>        <C>          <C>          <C>          <C>
THREE MONTHS ENDED
  SEPTEMBER 30, 1998:
    Ninety percent of gross
      proceeds.......................  $ 242,529  $   697,366  $   (2,509)   $158,565    $ 1,095,951
    Less ninety percent of --
      Operating expenditures.........    (78,729)    (281,960)   (144,102)    (35,891)      (540,682)
      Capital costs recovered........     --          --           --          --            --
      Accrual for future abandonment
         costs.......................    (11,727)      (1,500)     (5,848)       (925)       (20,000)
                                       ---------  -----------  ----------   ----------   -----------
    Net proceeds (excess costs)......  $ 152,073  $   413,906  $ (152,459)   $121,749    $   535,269
                                       =========  ===========  ==========   ==========   ===========
    Trust share of net proceeds
      (99.99%).......................                                                    $   535,215
                                                                                         ===========
    Production Volumes and Average
      Prices:
      Crude oil, condensate and
         natural gas liquids
         (Bbls)......................        127       23,391      --           1,635         25,153
                                       =========  ===========  ==========   ==========   ===========
      Average sales price per Bbl....  $    9.53  $     11.11  $   --        $  24.87    $     12.00
                                       =========  ===========  ==========   ==========   ===========
      Natural gas (Mcf)..............    110,908      186,887      (2,613)     63,819        359,001
                                       =========  ===========  ==========   ==========   ===========
      Average sales price per Mcf....  $    2.18  $      2.34  $      .96    $   1.85    $      2.21
                                       =========  ===========  ==========   ==========   ===========
    Producing wells..................          3            3           3           1             10
</TABLE>

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

o   The amounts shown are for Mesa Offshore Royalty Partnership.

o   The amounts for the three months ended September 30, 1999 and 1998 represent
    actual production for the periods May 1999 through July 1999 and May 1998
    through July 1998, respectively.

o   Capital costs recovered represent capital costs incurred during the current
    or prior periods to the extent that such costs have been recovered by PNR
    from current period Gross Proceeds.

o   Producing wells indicate the number of wells capable of production as of the
    end of the period.

o   West Delta 61 and 62 have ceased production since the second quarter of
    1998. However, operating expenses were still being incurred for maintenance
    procedures. In the third quarter 1999, the Trust began receiving revenues
    from new wells.

o   PNR advised the Trust during second quarter of 1999 that no additional
    future abandonment costs will be withheld from the Trust based on its
    current estimates of future abandonment costs for the Trust properties.

                                       9
<PAGE>

<TABLE>
<CAPTION>
                                                      SOUTH
                                         BRAZOS       MARSH        WEST      MATAGORDA
                                        A-7 AND     ISLAND 155   DELTA 61     ISLAND
                                          A-39       AND 156      AND 62        624         TOTAL
                                        --------    ----------   ---------   ---------   -----------
<S>                                     <C>         <C>          <C>         <C>         <C>
NINE MONTHS ENDED
  SEPTEMBER 30, 1999:
    Ninety percent of gross
      proceeds.......................   $951,282    $   74,684   $ 616,837   $ 240,457   $ 1,883,260
    Release of MMS royalty reserve...      --        2,116,594      --          --         2,116,594
    Less ninety percent of --
      Operating expenditures.........   (291,596)     (278,470)   (315,777)   (112,589)     (998,432)
      Capital costs recovered........     (4,099)      (61,458)     --          (5,625)      (71,182)
      Accrual for future abandonment
      costs..........................    (11,727)      (34,796)     (5,848)       (925)      (53,296)
                                        --------    ----------   ---------   ---------   -----------
    Net proceeds (excess costs)......   $643,860    $1,816,554   $ 295,212   $ 121,318   $ 2,876,944
                                        ========    ==========   =========   =========   ===========
    Trust share of net proceeds
      (99.99%).......................                                                    $ 2,876,656
                                                                                         ===========
    Production Volumes and Average
      Prices:
      Crude oil, condensate and
         natural gas liquids
         (Bbls)......................        302         7,519       8,191       2,018        18,030
                                        ========    ==========   =========   =========   ===========
      Average sales price per Bbl....   $  17.85    $    10.94   $   16.41   $   11.55   $     13.60
                                        ========    ==========   =========   =========   ===========
      Natural gas (Mcf)..............    507,039        27,510     197,717     122,356       854,622
                                        ========    ==========   =========   =========   ===========
      Average sales price per Mcf....   $   1.87    $    (0.27)  $    2.44   $    1.77   $      1.92
                                        ========    ==========   =========   =========   ===========
    Producing wells..................
</TABLE>

<TABLE>
<CAPTION>
                                                       SOUTH
                                         BRAZOS        MARSH         WEST      MATAGORDA
                                         A-7 AND     ISLAND 155    DELTA 61     ISLAND
                                          A-39        AND 156       AND 62        624         TOTAL
                                        ---------    ----------   ----------   ---------   -----------
<S>                                     <C>          <C>          <C>          <C>         <C>
NINE MONTHS ENDED
  SEPTEMBER 30, 1998:
    Ninety percent of gross
      proceeds.......................   $ 800,332    $1,422,381   $  452,700   $ 720,753   $ 3,396,166
    Less ninety percent of --
      Operating expenditures.........    (236,107)     (789,506)    (500,112)   (137,902)   (1,663,627)
      Capital costs recovered........      --            --           --          (1,883)       (1,883)
      Accrual for future abandonment
         costs.......................     (35,181)       (4,499)     (17,544)     (2,776)      (60,000)
                                        ---------    ----------   ----------   ---------   -----------
    Net proceeds (excess costs)......   $ 529,044    $  628,376   $  (64,956)  $ 578,192   $ 1,670,656
                                        =========    ==========   ==========   =========   ===========
    Trust share of net proceeds
      (99.99%).......................                                                      $ 1,670,489
                                                                                           ===========
    Production Volumes and Average
      Prices:
      Crude oil, condensate and
         natural gas liquids
         (Bbls)......................         560        43,643          594       4,796        49,593
                                        =========    ==========   ==========   =========   ===========
      Average sales price per Bbl....   $   12.76    $    12.53   $    15.51   $   18.24   $     13.12
                                        =========    ==========   ==========   =========   ===========
      Natural gas (Mcf)..............     344,684       369,828      170,106     280,048     1,164,666
                                        =========    ==========   ==========   =========   ===========
      Average sales price per Mcf....   $    2.30    $     2.37   $     2.61   $    2.26   $      2.36
                                        =========    ==========   ==========   =========   ===========
    Producing wells..................           3             3            3           1            10
</TABLE>

------------
o   The amounts shown are for Mesa Offshore Royalty Partnership.

o   The amounts for the nine months ended September 30, 1999 and 1998 represent
    actual production for the periods November 1998 through July 1999, and
    November 1997 through July 1998, respectively.

o   Capital costs recovered represent capital costs incurred during the current
    or prior periods to the extent that such costs have been recovered by PNR
    from current period Gross Proceeds.

o   Producing wells indicate the number of wells capable of production as of the
    end of the period.

o   West Delta 61 and 62 have ceased production since the second quarter of
    1998. However, operating expenses were being incurred for maintenance
    procedures. In the third quarter 1999, the Trust began receiving revenues
    from new wells.

o   The release of MMS royalty reserve included in the nine months ended
    September 30, 1999 relates to a refund by PNR to the Trust of $3.1 million
    after settling all known disputes with the MMS involving Trust properties,
    reduced by the cost carryforward of $1.0 million that existed at the time of
    the refund (see "Operational Review" in "Item 2. Management's Discussion
    and Analysis of Financial Condition and Results of Operations").

o   PNR advised the Trust during second quarter of 1999 that no additional
    future abandonment costs will be withheld from the Trust based on its
    current estimates of future abandonment costs for the Trust properties.

                                       10
<PAGE>
                                    PART II

ITEM 6.  EXHIBIT AND REPORTS ON FORM 8-K

     (A)  EXHIBITS

     (Asterisk indicates exhibit previously filed with the Securities and
Exchange Commission and incorporated herein by reference.)

<TABLE>
<CAPTION>
                                                                                                 SEC FILE
                                                                                                    OR
                                                                                               REGISTRATION    EXHIBIT
                                                                                                  NUMBER       NUMBER
                                                                                               ------------    -------
<C>                <S>                                                                         <C>             <C>
       4(a)        *Mesa Offshore Trust Indenture between Mesa Petroleum Co. and Texas
                    Commerce Bank National Association, as Trustee, dated December 15,
                    1982....................................................................      2-79673         10(gg)
       4(b)        *Overriding Royalty Conveyance between Mesa Petroleum Co. and Mesa
                    Offshore Royalty Partnership, dated December 15, 1982...................      2-79673         10(hh)
       4(c)        *Partnership Agreement between Mesa Offshore Management Co. and Texas
                    Commerce Bank National Association, as Trustee, dated December 15,
                    1982....................................................................      2-79673         10(ii)
       4(d)        *Amendment to Partnership Agreement between Mesa Offshore Management Co.,
                    Texas Commerce Bank National Association, as Trustee, and Mesa Operating
                    Limited Partnership, dated December 27, 1985 (Exhibit 4(d) to Form 10-K
                    for year ended December 31, 1992 of Mesa Offshore Trust)................       1-8432          4(d)
       4(e)        *Amendment to Partnership Agreement between Texas Commerce Bank National
                    Association, as Trustee and Mesa Operating Limited Partnership dated as
                    of January 5, 1994 (Exhibit 4(e) to Form 10-K for year ended December
                    31, 1993 of Mesa Offshore Trust)........................................       1-8432          4(e)
         27         Financial Data Schedule
</TABLE>

     (B)  REPORTS ON FORM 8-K

          None.

                                       11
<PAGE>
                                   SIGNATURES

     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.

                                          MESA OFFSHORE TRUST

                                                 CHASE BANK OF TEXAS,
                                          By     NATIONAL ASSOCIATION
                                             ---------------------------------
                                                 TRUSTEE

                                          By /s/ PETE FOSTER
                                             ---------------------------------
                                                 Pete Foster
                                                 SENIOR VICE PRESIDENT & TRUST
                                                 OFFICER

Date:  November 12, 1999

     The Registrant, Mesa Offshore Trust, has no principal executive officer,
principal financial officer, board of directors or persons performing similar
functions. Accordingly, no additional signatures are available and none have
been provided.

                                       12