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                                FORM 10-Q


                    SECURITIES AND EXCHANGE COMMISSION
                         WASHINGTON, D.C.  20549

(MARK ONE)

(X)  QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
     OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended March 31, 2000

                                    OR

( )  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)
     OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from ________________ to ________________

Commission File Number 0-20298

         SOUTHWEST ROYALTIES INSTITUTIONAL 1990-91 INCOME PROGRAM
         Southwest Royalties Institutional Income Fund X-C, L.P.
                  (Exact name of registrant as specified
                  in its limited partnership agreement)

Delaware                                    75-2374449
(State or other jurisdiction of                (I.R.S. Employer
incorporation or organization)                Identification No.)


                       407 N. Big Spring, Suite 300
                           Midland, Texas 79701
                 (Address of principal executive offices)

                             (915) 686-9927
                     (Registrant's telephone number,
                           including area code)

Indicate  by  check  mark  whether 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

        The total number of pages contained in this report is 13.

<PAGE>
                     PART I. - FINANCIAL INFORMATION


Item 1.   Financial Statements

The  unaudited  condensed financial statements included  herein  have  been
prepared  by  the Registrant (herein also referred to as the "Partnership")
in  accordance  with generally accepted accounting principles  for  interim
financial information and with the instructions to Form 10-Q and Rule 10-01
of Regulation S-X.  Accordingly, they do not include all of the information
and  footnotes  required  by generally accepted accounting  principles  for
complete   financial  statements.   In  the  opinion  of  management,   all
adjustments necessary for a fair presentation have been included and are of
a  normal  recurring nature.  The financial statements should  be  read  in
conjunction with the audited financial statements and the notes thereto for
the  year ended December 31, 1999 which are found in the Registrant's  Form
10-K  Report  for  1999 filed with the Securities and Exchange  Commission.
The December 31, 1999 balance sheet included herein has been taken from the
Registrant's 1999 Form 10-K Report.  Operating results for the three  month
period  ended March 31, 2000 are not necessarily indicative of the  results
that may be expected for the full year.

<PAGE>
         Southwest Royalties Institutional Income Fund X-C, L.P.

                              Balance Sheets


                                                 March 31,     December 31,
                                                    2000           1999
                                                 ---------     ------------
                                                (unaudited)

  Assets

Current assets:
 Cash and cash equivalents                    $     40,598         22,098
 Receivable from Managing General Partner          102,634        113,004
                                                 ---------      ---------
    Total current assets                           143,232        135,102
                                                 ---------      ---------
Oil and gas properties - using the
 full-cost method of accounting                  2,221,662      2,221,662
  Less accumulated depreciation,
   depletion and amortization                    1,940,479      1,929,479
                                                 ---------      ---------
    Net oil and gas properties                     281,183        292,183
                                                 ---------      ---------
                                              $    424,415        427,285
                                                 =========      =========

  Liabilities and Partners' Equity

Current liability - Distribution payable      $          2              2
                                                 ---------      ---------
Partners' equity:
 General partners                                 (17,726)       (18,539)
 Limited partners                                  442,139        445,822
                                                 ---------      ---------
    Total partners' equity                         424,413        427,283
                                                 ---------      ---------
                                              $    424,415        427,285
                                                 =========      =========

<PAGE>
         Southwest Royalties Institutional Income Fund X-C, L.P.

                         Statements of Operations
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          2000      1999
                                                          ----      ----

  Revenues

Income from net profits interests                   $    73,025   (10,049)
Interest                                                    452         63
                                                        -------    -------
                                                         73,477    (9,986)
                                                        -------    -------
  Expenses

General and administrative                               10,347     11,203
Depreciation, depletion and amortization                 11,000     20,000
                                                        -------    -------
                                                         21,347     31,203
                                                        -------    -------
Net income (loss)                                   $    52,130   (41,189)
                                                        =======    =======
Net income (loss) allocated to:

 Managing General Partner                           $     5,682    (1,907)
                                                        =======    =======
 General partner                                    $       631      (212)
                                                        =======    =======
 Limited partners                                   $    45,817   (39,070)
                                                        =======    =======
  Per limited partner unit                          $      7.66      (6.53)
                                                        =======    =======

<PAGE>
         Southwest Royalties Institutional Income Fund X-C, L.P.

                         Statements of Cash Flows
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          2000      1999
                                                          ----      ----

Cash flows from operating activities:

 Cash received from net profits interest            $    77,721      1,723
 Cash paid to suppliers                                 (4,673)   (11,562)
 Interest received                                          452         63
                                                       --------   --------
   Net cash provided by (used in) operating activities               73,500
(9,776)
                                                       --------   --------

Cash flows provided by investing activities

 Sale of oil and gas properties                               -     18,643
                                                       --------   --------
Cash flows used in financing activities:

 Distributions to partners                             (55,000)          -
                                                       --------   --------
Net increase in cash and cash equivalents                18,500      8,867

 Beginning of period                                     22,098      5,341
                                                       --------   --------
 End of period                                      $    40,598     14,208
                                                       ========   ========

                                                               (continued)

<PAGE>
         Southwest Royalties Institutional Income Fund X-C, L.P.

                   Statements of Cash Flows, continued
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          2000      1999
                                                          ----      ----

Reconciliation of net income (loss) to net cash
  provided by (used in) operating activities:

Net income (loss)                                   $    52,130   (41,189)

Adjustments to reconcile net income (loss) to net cash
  provided by (used in) operating activities:

  Depreciation, depletion and amortization               11,000     20,000
  Decrease in receivables                                 4,696     11,772
  (Decrease) increase in payables                         5,674      (359)
                                                        -------    -------
Net cash provided by (used in) operating activities $    73,500    (9,776)
                                                        =======    =======

<PAGE>
         Southwest Royalties Institutional Income Fund X-C, L.P.
                     (a Delaware limited partnership)

                      Notes to Financial Statements


1.   Organization
     Southwest  Royalties Institutional Income Fund X-C, L.P. was organized
     under the laws of the state of Delaware on September 20, 1991, for the
     purpose  of acquiring producing oil and gas properties and to  produce
     and market crude oil and natural gas produced from such properties for
     a  term  of 50 years, unless terminated at an earlier date as provided
     for  in the Partnership Agreement.  The Partnership sells its oil  and
     gas production to several purchasers with the prices it receives being
     dependent  upon  the oil and gas economy.  Southwest  Royalties,  Inc.
     serves as the Managing General Partner and H. H. Wommack, III, as  the
     individual   general  partner.   Revenues,  costs  and  expenses   are
     allocated as follows:

                                                     Limited      General
                                                     Partners     Partners
                                                     --------     --------
     Interest income on capital contributions       100%             -
     Oil and gas sales                               90%           10%
     All other revenues                              90%           10%
     Organization and offering costs (1)            100%             -
     Syndication costs                              100%             -
     Amortization of organization costs             100%             -
     Property acquisition costs                     100%             -
     Gain/loss on property disposition               90%           10%
     Operating and administrative costs (2)          90%           10%
     Depreciation, depletion and amortization
      of oil and gas properties                     100%             -
     All other costs                                 90%           10%

          (1)   All  organization costs in excess of 3% of initial  capital
          contributions  will be paid by the Managing General  Partner  and
          will  be treated as a capital contribution.  The Partnership paid
          the  Managing  General Partner an amount equal to 3%  of  initial
          capital contributions for such organization costs.

          (2)   Administrative costs in any year which exceed 2% of capital
          contributions shall be paid by the Managing General  Partner  and
          will be treated as a capital contribution.

2.   Summary of Significant Accounting Policies
     The  interim financial information as of March 31, 2000, and  for  the
     three  months ended March 31, 2000, is unaudited.  Certain information
     and  footnote  disclosures 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.   However,
     in  the  opinion  of  management, these interim  financial  statements
     include all the necessary adjustments to fairly present the results of
     the interim periods and all such adjustments are of a normal recurring
     nature.  The interim consolidated financial statements should be  read
     in  conjunction  with the audited financial statements  for  the  year
     ended December 31, 1999.

<PAGE>

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

General

Southwest Royalties Institutional Income Fund X-C, L.P. was organized as  a
Delaware limited partnership on September 20, 1991.  The offering  of  such
limited  partnership interests began October 1, 1991 as  part  of  a  shelf
offering registered under the name Southwest Royalties Institutional  1990-
91  Income Program.  Minimum capital requirements for the Partnership  were
met on January 28, 1992, with the offering of limited partnership interests
concluding April 30, 1992.

The Partnership was formed to acquire royalty and net profits interests  in
producing  oil  and  gas properties, to produce and market  crude  oil  and
natural  gas  produced  from such properties, and  to  distribute  the  net
proceeds from operations to the limited and general partners.  Net revenues
from  producing  oil  and gas properties will not be  reinvested  in  other
revenue  producing  assets except to the extent that production  facilities
and wells are improved or reworked or where methods are employed to improve
or enable more efficient recovery of oil and gas reserves.

Increases   or   decreases   in  Partnership   revenues   and,   therefore,
distributions  to partners will depend primarily on changes in  the  prices
received  for  production,  changes in volumes of  production  sold,  lease
operating  expenses, enhanced recovery projects, offset drilling activities
pursuant  to farm-out arrangements, sales of properties, and the  depletion
of  wells.   Since  wells deplete over time, production  can  generally  be
expected to decline from year to year.

Well  operating costs and general and administrative costs usually decrease
with   production   declines;  however,  these  costs  may   not   decrease
proportionately.  Net income available for distribution to the partners  is
therefore expected to fluctuate in later years based on these factors.

Based  on  current  conditions, management does not  anticipate  performing
workovers during the year to enhance production.

Oil and Gas Properties

Oil  and  gas  properties  are accounted for at cost  under  the  full-cost
method.  Under this method, all productive and nonproductive costs incurred
in  connection with the acquisition, exploration and development of oil and
gas  reserves  are capitalized.  Gain or loss on the sale of  oil  and  gas
properties  is not recognized unless significant oil and gas  reserves  are
involved.

The  Partnership's policy for depreciation, depletion and  amortization  of
oil  and  gas  properties is computed under the units  of  revenue  method.
Under the units of revenue method, depreciation, depletion and amortization
is  computed  on  the  basis of current gross revenues from  production  in
relation  to future gross revenues, based on current prices, from estimated
production of proved oil and gas reserves.

Should the net capitalized costs exceed the estimated present value of  oil
and gas reserves, discounted at 10%, such excess costs would be charged  to
current  expense.  As of March 31, 2000, the net capitalized costs did  not
exceed the estimated present value of oil and gas reserves.

<PAGE>
Results of Operations

A.  General Comparison of the Quarters Ended March 31, 2000 and 1999

The  following  table  provides certain information  regarding  performance
factors for the quarters ended March 31, 2000 and 1999.

                                               Three Months
                                                  Ended         Percentage
                                                March 31,        Increase
                                              2000      1999    (Decrease)
                                              ----      ----    ----------
Average price per barrel of oil           $   25.66      9.43     172%
Average price per mcf of gas              $    1.82      1.58      15%
Oil production in barrels                     8,100     9,500    (15%)
Gas production in mcf                         8,600    11,900    (28%)
Income from net profits interests         $  73,025  (10,049)     827%
Partnership distributions                 $  55,000         -     100%
Limited partner distributions             $  49,500         -     100%
Per unit distribution to limited
 partners                                 $    8.27         -     100%
Number of limited partner units               5,983     5,983

Revenues

The  Partnership's income from net profits interests increased  to  $73,025
from   $(10,049)  for  the  quarters  ended  March  31,  2000   and   1999,
respectively,  an  increase of 827%. The principal  factors  affecting  the
comparison of the quarters ended March 31, 2000 and 1999 are as follows:

1.  The  average  price  for a barrel of oil received  by  the  Partnership
    increased  during the quarter ended March 31, 2000 as compared  to  the
    quarter  ended March 31, 1999 by 172%, or $16.23 per barrel,  resulting
    in  an  increase of approximately $154,200 in income from  net  profits
    interests.  Oil sales represented 93% of total oil and gas sales during
    the  quarter ended March 31, 2000 as compared to 83% during the quarter
    ended March 31, 1999.

    The  average  price  for  an  mcf of gas received  by  the  Partnership
    increased during the same period by 15%, or $.24 per mcf, resulting  in
    an  increase  of  approximately  $2,900  in  income  from  net  profits
    interests.

    The  total  increase in income from net profits interests  due  to  the
    change  in prices received from oil and gas production is approximately
    $157,100.  The market price for oil and gas has been extremely volatile
    over  the  past  decade, and management expects  a  certain  amount  of
    volatility to continue in the foreseeable future.

<PAGE>
2.  Oil  production decreased approximately 1,400 barrels or 15% during the
    quarter ended March 31, 2000 as compared to the quarter ended March 31,
    1999,  resulting in a decrease of approximately $35,900 in income  from
    net profits interests.

    Gas production decreased approximately 3,300 mcf or 28% during the same
    period, resulting in a decrease of approximately $6,000 in income  from
    net profits interests.

    The  total  decrease in income from net profits interests  due  to  the
    change  in  production  is  approximately  $41,900.   The  decrease  is
    primarily a result of one major gas well ceasing to produce, a workover
    is to be performed.

3.  Lease  operating  costs  and  production  taxes  were  27%  higher,  or
    approximately $32,000 more during the quarter ended March 31,  2000  as
    compared to the quarter ended March 31, 1999.  The increase is due to a
    workover, major repairs and maintenance performed in 2000.

Costs and Expenses

Total costs and expenses decreased to $21,347 from $31,203 for the quarters
ended  March  31,  2000  and 1999, respectively, a decrease  of  32%.   The
decrease  is  the  result of lower general and administrative  expense  and
depletion expense.

1.  General and administrative costs consists of independent accounting and
    engineering  fees,  computer services, postage,  and  Managing  General
    Partner personnel costs.  General and administrative costs decreased 8%
    or  approximately  $900  during the quarter ended  March  31,  2000  as
    compared to the quarter ended March 31, 1999.

2.  Depletion expense decreased to $11,000 for the quarter ended March  31,
    2000  from  $20,000  for the same period in 1999.   This  represents  a
    decrease  of 45%.  Depletion is calculated using the units  of  revenue
    method  of  amortization based on a percentage of current period  gross
    revenues  to  total future gross oil and gas revenues, as estimated  by
    the  Partnership's independent petroleum consultants.   A  contributing
    factor  to  the  decrease in depletion expense between the  comparative
    periods  was  the  increase in the price of oil used to  determine  the
    Partnership's reserves, and the increase in oil and gas sales.

<PAGE>
Liquidity and Capital Resources

The  primary source of cash is from operations, the receipt of income  from
interests in oil and gas properties.  The Partnership knows of no  material
change, nor does it anticipate any such change.

Cash  flows  provided by (used in) operating activities were  approximately
$73,500  in  the quarter ended March 31, 2000 as compared to  approximately
$(9,800)  in the quarter ended March 31, 1999.  The primary source  of  the
2000 cash flow from operating activities was profitable operations.

There  were  no cash flows provided by investing activities in the  quarter
ended  March  31,  2000. Cash flows provided by investing  activities  were
approximately $18,600 in the quarter ended March 31, 1999.

Cash  flows used in financing activities were approximately $55,000 in  the
quarter  ended March 31, 2000.  There were no cash flows used in  financing
activities in the quarter ended March 31, 1999.

Total distributions during the quarter ended March 31, 2000 were $55,000 of
which  $49,500  was distributed to the limited partners and $5,500  to  the
general partners.  The per unit distribution to limited partners during the
quarter ended March 31, 2000 was $8.27.  There were no distributions during
the quarter ended March 31, 1999.

The  primary sources for the 2000 distributions of $55,000 were oil and gas
operations  of  approximately  $73,500,  resulting  in  excess   cash   for
contingencies or subsequent distributions to partners.

Since  inception of the Partnership, cumulative monthly cash  distributions
of  $2,702,245  have  been made to the partners.  As  of  March  31,  2000,
$2,445,505 or $408.74 per limited partner unit has been distributed to  the
limited partners, representing a 82% return of the capital contributed.

As of March 31, 2000, the Partnership had approximately $143,200 in working
capital.   The  Managing  General Partner knows of no  unusual  contractual
commitments  and  believes  the  revenues  generated  from  operations  are
adequate to meet the needs of the Partnership.

Liquidity - Managing General Partner

The  Managing General Partner has a highly leveraged capital structure with
over  $50.1  million principal and $17.5 million interest payments  due  in
2000  on  its  debt  obligations. Due to the severely  depressed  commodity
prices  experienced  during the last quarter of 1997, throughout  1998  and
continuing through the second quarter of 1999 the Managing General  Partner
is  experiencing difficulty in generating sufficient cash flow to meet  its
obligations  and sustain its operations.  The Managing General  Partner  is
currently  in  the  process  of renegotiating  the  terms  of  its  various
obligations  with its creditors and/or attempting to seek  new  lenders  or
equity  investors.   Additionally,  the  Managing  General  Partner   would
consider disposing of certain assets in order to meet its obligations.

There  can  be  no  assurance  that  the Managing  General  Partner's  debt
restructuring efforts will be successful or that the lenders will agree  to
a   course   of  action  consistent  with  the  Managing  General  Partners
requirements  in restructuring the obligations.  Even if such agreement  is
reached,  it  may  require approval of additional  lenders,  which  is  not
assured.  Furthermore, there can be no assurance that the sales  of  assets
can  be  successfully  accomplished on terms  acceptable  to  the  Managing
General   Partner.   Under  current  circumstances,  the  Managing  General
Partner's  ability to continue as a going concern depends upon its  ability
to  (1)  successfully  restructure  its obligations  or  obtain  additional
financing  as  may  be  required, (2) maintain  compliance  with  all  debt
covenants, (3) generate sufficient cash flow to meet its obligations  on  a
timely  basis, and (4) achieve satisfactory levels of future earnings.   If
the  Managing  General Partner is unsuccessful in its efforts,  it  may  be
unable to meet its obligations making it necessary to undertake such  other
actions as may be appropriate to preserve asset values.


<PAGE>
                       PART II. - OTHER INFORMATION


Item 1.   Legal Proceedings

          None

Item 2.   Changes in Securities

          None

Item 3.   Defaults Upon Senior Securities

          None

Item 4.   Submission of Matter to a Vote of Security Holders

          None

Item 5.   Other Information

          None

Item 6.   Exhibits and Reports on Form 8-K

          (a) Exhibits:

               27 Financial Data Schedule

               (b)  Report on Form 8-K:

                     No  reports on Form 8-K were filed during the  quarter
               for which this report is filed.

<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.


                              SOUTHWEST ROYALTIES INSTITUTIONAL
                              INCOME FUND X-C, L.P.
                              a Delaware limited partnership


                              By:  Southwest Royalties, Inc.
                                   Managing General Partner


                              By:  /s/ J Steven Person
                                   ------------------------------
                                   J Steven Person, Vice-President of
                                   Marketing and Chief Financial Officer
                                   of Southwest Royalties, Inc.
                                   the Managing General Partner



Date:  May 15, 2000

<PAGE>