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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, 1998

                                    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, 1997 which are found in the Registrant's  Form
10-K  Report  for  1997 filed with the Securities and Exchange  Commission.
The December 31, 1997 balance sheet included herein has been taken from the
Registrant's 1997 Form 10-K Report.  Operating results for the three  month
period  ended March 31, 1998 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,
                                                    1998           1997
                                                 ---------     ------------
                                                (unaudited)

  Assets

Current assets:
 Cash and cash equivalents                    $      4,447         20,066
 Receivable from Managing General Partner           54,548        105,891
                                                 ---------      ---------
    Total current assets                            58,995        125,957
                                                 ---------      ---------
Oil and gas properties - using the
 full-cost method of accounting                  2,244,628      2,244,628
  Less accumulated depreciation,
   depletion and amortization                    1,732,479      1,703,479
                                                 ---------      ---------
    Net oil and gas properties                     512,149        541,149
                                                 ---------      ---------
                                              $    571,144        667,106
                                                 =========      =========

  Liabilities and Partners' Equity

Partners' equity:
 General partners                             $   (25,482)       (18,785)
 Limited partners                                  596,626        685,891
                                                 ---------      ---------
    Total partners' equity                         571,144        667,106
                                                 ---------      ---------
                                              $    571,144        667,106
                                                 =========      =========

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

                         Statements of Operations
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          1998      1997
                                                          ----      ----

  Revenues

Income from net profits interests                   $    27,615    128,470
Interest                                                    400      1,295
                                                        -------    -------
                                                         28,015    129,765
                                                        -------    -------
  Expenses

General and administrative                               16,977     15,558
Depreciation, depletion and amortization                 29,000     24,000
                                                        -------    -------
                                                         45,977     39,558
                                                        -------    -------
Net income (loss)                                   $  (17,962)     90,207
                                                        =======    =======
Net income (loss) allocated to:

 Managing General Partner                           $       993     10,279
                                                        =======    =======
 General partner                                    $       110      1,142
                                                        =======    =======
 Limited partners                                   $  (19,065)     78,786
                                                        =======    =======
  Per limited partner unit                          $    (3.19)      13.17
                                                        =======    =======

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

                         Statements of Cash Flows
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          1998      1997
                                                          ----      ----

Cash flows from operating activities:

 Cash received from net profits interest            $    77,490    151,355
 Cash paid to suppliers                                (15,509)   (11,108)
 Interest received                                          400      1,295
                                                       --------   --------
  Net cash provided by operating activities              62,381    141,542
                                                       --------   --------
Cash flows used in financing activities:

 Distributions to partners                             (78,000)  (182,500)
                                                       --------   --------
Net decrease in cash and cash equivalents              (15,619)   (40,958)

 Beginning of period                                     20,066    170,421
                                                       --------   --------
 End of period                                      $     4,447    129,463
                                                       ========   ========

                                                               (continued)

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

                   Statements of Cash Flows, continued
                               (unaudited)


                                                        Three Months Ended
                                                            March 31,
                                                          1998      1997
                                                          ----      ----

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

Net income (loss)                                   $  (17,962)     90,207

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

  Depreciation, depletion and amortization               29,000     24,000
  Decrease in receivables                                49,875     22,885
  Increase in payables                                    1,468      4,450
                                                        -------    -------
Net cash provided by operating activities           $    62,381    141,542
                                                        =======    =======

<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, 1998, and  for  the
     three  months ended March 31, 1998, 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, 1997.

<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 anticipates performing  workovers
during  the  next  few years to enhance production.  The Partnership  could
possibly  experience  the  following changes; a  little  less  than  normal
decline in 1998 and thereafter a lower than normal decline.

<PAGE>
Results of Operations

A.  General Comparison of the Quarters Ended March 31, 1998 and 1997

The  following  table  provides certain information  regarding  performance
factors for the quarters ended March 31, 1998 and 1997.

                                               Three Months
                                                  Ended         Percentage
                                                March 31,        Increase
                                              1998      1997    (Decrease)
                                              ----      ----    ----------
Average price per barrel of oil           $   12.55     22.18    (44%)
Average price per mcf of gas              $    1.60      2.75    (42%)
Oil production in barrels                    11,600    10,300      13%
Gas production in mcf                        18,700    17,100      10%
Income from net profits interests         $  27,615   128,470    (79%)
Partnership distributions                 $  78,000   182,500    (58%)
Limited partner distributions             $  70,200   164,250    (58%)
Per unit distribution to limited
 partners                                 $   11.73     27.45    (58%)
Number of limited partner units               5,983     5,983

Revenues

The  Partnership's income from net profits interests decreased  to  $27,615
from $128,470 for the quarters ended March 31, 1998 and 1997, respectively,
a  decrease of 79%. The principal factors affecting the comparison  of  the
quarters ended March 31, 1998 and 1997 are as follows:

1.  The  average  price  for a barrel of oil received  by  the  Partnership
    decreased  during the quarter ended March 31, 1998 as compared  to  the
    quarter ended March 31, 1997 by 44%, or $9.63 per barrel, resulting  in
    a  decrease  of  approximately  $99,200  in  income  from  net  profits
    interests.  Oil sales represented 83% of total oil and gas sales during
    the  quarter ended March 31, 1998 as compared to 83% during the quarter
    ended March 31, 1997.

    The  average  price  for  an  mcf of gas received  by  the  Partnership
    decreased during the same period by 42%, or $1.15 per mcf, resulting in
    a  decrease  of  approximately  $19,700  in  income  from  net  profits
    interests.

    The  total  decrease in income from net profits interests  due  to  the
    change  in prices received from oil and gas production is approximately
    $118,900.  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 increased approximately 1,300 barrels or 13% during the
    quarter ended March 31, 1998 as compared to the quarter ended March 31,
    1997, resulting in an increase of approximately $16,300 in income  from
    net profits interests.

    Gas production increased approximately 1,600 mcf or 10% during the same
    period, resulting in an increase of approximately $2,600 in income from
    net profits interests.

    The  total  increase in income from net profits interests  due  to  the
    change in production is approximately $18,900.

3.  Lease  operating  costs  and  production  taxes  were  1%  higher,   or
    approximately  $900 more during the quarter ended  March  31,  1998  as
    compared to the quarter ended March 31, 1997.

Costs and Expenses

Total costs and expenses increased to $45,977 from $39,558 for the quarters
ended  March  31,  1998 and 1997, respectively, an increase  of  17%.   The
increase  is  the result of higher 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  increased
    10% or approximately $1,400 during the quarter ended March 31, 1998  as
    compared to the quarter ended March 31, 1997.

2.  Depletion expense increased to $29,000 for the quarter ended March  31,
    1998  from  $24,000  for the same period in 1997.  This  represents  an
    increase  of 18%.  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  increase in depletion expense between the  comparative
    periods  was  the  decrease in the price of oil used to  determine  the
    Partnership's reserves for January 1, 1998 as compared to 1997.

<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 operating activities were approximately $62,400  in
the  quarter ended March 31, 1998 as compared to approximately $141,500  in
the quarter ended March 31, 1997.  The primary source of the 1998 cash flow
from operating activities was profitable operations.

Cash  flows used in financing activities were approximately $78,000 in  the
quarter ended March 31, 1998 as compared to approximately $114,300  in  the
quarter ended March 31, 1997.  The only use in financing activities was the
distributions to partners.

Total distributions during the quarter ended March 31, 1998 were $78,000 of
which  $70,200  was distributed to the limited partners and $7,800  to  the
general partners.  The per unit distribution to limited partners during the
quarter  ended March 31, 1998 was $11.73.  Total distributions  during  the
quarter  ended  March  31,  1997  were  $182,500  of  which  $164,250   was
distributed  to  the limited partners and $18,250 to the general  partners.
The  per  unit  distribution to limited partners during the  quarter  ended
March 31, 1997 was $27.45.

The  primary sources for the 1998 distributions of $78,000 were oil and gas
operations of approximately $62,400.  The source for the 1997 distributions
of  $182,500 was oil and gas operations of approximately $141,500, with the
balance from available cash on hand at the beginning of the period.

Since  inception of the Partnership, cumulative monthly cash  distributions
of  $2,535,468  have  been made to the partners.  As  of  March  31,  1998,
$2,293,778 or $383.38 per limited partner unit has been distributed to  the
limited partners, representing a 77% return of the capital contributed.

As  of March 31, 1998, the Partnership had approximately $59,000 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.

<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/ Bill E. Coggin
                                   ------------------------------
                                   Bill E. Coggin, Vice President
                                   and Chief Financial Officer


Date:  May 15, 1998

<PAGE>