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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 June 30, 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 14.

<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  and
six month periods ended June 30, 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


                                                 June 30,      December 31,
                                                   1998            1997
                                                ---------      ------------
                                               (unaudited)

  Assets

Current assets:
 Cash and cash equivalents                   $      5,539          20,066
 Receivable from Managing General Partner          52,032         105,891
                                                ---------       ---------
    Total current assets                           57,571         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                   1,764,479       1,703,479
                                                ---------       ---------
    Net oil and gas properties                    480,149         541,149
                                                ---------       ---------
                                             $    537,720         667,106
                                                =========       =========
  Liabilities and Partners' Equity

Partners' equity:
 General partners                            $   (25,624)        (18,785)
 Limited partners                                 563,344         685,891
                                                ---------       ---------
    Total partners' equity                        537,720         667,106
                                                ---------       ---------
                                             $    537,720         667,106
                                                =========       =========

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

                         Statements of Operations
                               (unaudited)


                                 Three Months Ended      Six Months Ended
                                       June 30,              June 30,
                                    1998      1997        1998      1997

  Revenues

Income from net profits
 interests                    $    22,618    101,923     50,233    230,393
Interest                              193      1,064        593      2,359
                                  -------    -------    -------    -------
                                   22,811    102,987     50,826    232,752
                                  -------    -------    -------    -------

  Expenses

General and administrative         12,236      9,653     29,213     25,211
Depreciation, depletion and
 amortization                      32,000     22,000     61,000     46,000
                                  -------    -------    -------    -------
                                   44,236     31,653     90,213     71,211
                                  -------    -------    -------    -------
Net income (loss)             $  (21,425)     71,334   (39,387)    161,541
                                  =======    =======    =======    =======
Net income (loss) allocated to:

 Managing General Partner     $       952      8,400      1,945     18,679
                                  =======    =======     ======    =======
 General Partner              $       106        933        216      2,075
                                  =======    =======    =======    =======
 Limited Partners             $  (22,483)     62,001   (41,548)    140,787
                                  =======    =======    =======    =======
  Per limited partner unit    $    (3.76)      10.36     (6.94)      23.53
                                  =======    =======    =======    =======

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

                         Statements of Cash Flows
                               (unaudited)


                                                        Six Months Ended
                                                             June 30,
                                                          1998      1997

Cash flows from operating activities:

 Cash received from income from net profits
  interests                                         $    92,344    259,782
 Cash paid to suppliers                                (17,465)   (25,096)
 Interest received                                          593      2,359
                                                        -------    -------
  Net cash provided by operating activities              75,472    237,045
                                                        -------    -------
Cash flows used in financing activities:

 Distributions to partners                             (89,999)  (356,500)
                                                        -------    -------

Net decrease in cash and cash equivalents              (14,527)  (119,455)

 Beginning of period                                     20,066    170,421
                                                        -------    -------
 End of period                                      $     5,539     50,966
                                                        =======    =======

                                                               (continued)

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

                   Statements of Cash Flows, continued
                               (unaudited)


                                                        Six Months Ended
                                                             June 30,
                                                          1998      1997

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

Net income (loss)                                   $  (39,387)    161,541

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

  Depreciation, depletion and  amortization              61,000     46,000
  Decrease in receivables                                42,111     29,389
  Increase in payables                                   11,748        115
                                                        -------    -------
Net cash provided by operating activities           $    75,472    237,045
                                                        =======    =======

<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, with 340 limited partners purchasing 5,983 units
for $2,991,500.

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 farmout 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  1998.  The Partnership could possibly experience  a  low
decline.

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 June 30, 1998, the net capitalized costs  did  not
exceed the estimated present value of oil and gas reserves.  A continuation
of the oil price environment experienced during the first half of 1998 will
have  an adverse affect on the Company's revenues and operating cash  flow.
Also,  further declines in oil prices could result in additional  decreases
in the carrying value of the Company's oil and gas properties.



<PAGE>
Results of Operations

A.  General Comparison of the Quarters Ended June 30, 1998 and 1997

The  following  table  provides certain information  regarding  performance
factors for the quarters ended June 30, 1998 and 1997:

                                               Three Months
                                                  Ended          Percentage
                                                 June 30,         Increase
                                              1998       1997    (Decrease)
                                              ----       ----    ----------

Average price per barrel of oil          $    10.86     17.95    (40%)
Average price per mcf of gas             $     2.03      2.16     (6%)
Oil production in barrels                    10,300    11,900    (13%)
Gas production in mcf                        15,200    19,400    (22%)
Income from net profits interests        $   22,618   101,923    (78%)
Partnership distributions                $   12,000   174,000    (93%)
Limited partner distributions            $   10,800   156,600    (93%)
Per unit distribution to limited
 partners                                $     1.81     26.17    (93%)
Number of limited partner units               5,983     5,983


Revenues

The  Partnership's income from net profits interests decreased  to  $22,618
from  $101,923 for the quarters ended June 30, 1998 and 1997, respectively,
a  decrease of 78%.  The principal factors affecting the comparison of  the
quarters ended June 30, 1998 and 1997 are as follows:

1.  The  average  price  for a barrel of oil received  by  the  Partnership
    decreased  during the quarter ended June 30, 1998 as  compared  to  the
    quarter ended June 30, 1997 by 40%, or $7.09 per barrel, resulting in a
    decrease of approximately $84,371 in income from net profits interests.
    Oil  sales  represented  78% of total oil  and  gas  sales  during  the
    quarters  ended  June 30, 1998 as compared to 84%  during  the  quarter
    ended June 30, 1997.

    The  average  price  for  an  mcf of gas received  by  the  Partnership
    decreased during the same period by 6%, or $.13 per mcf, resulting in a
    decrease of approximately $2,520 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
    $86,891.   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 1,600 barrels or 13% during the
    quarter  ended June 30, 1998 as compared to the quarter ended June  30,
    1997,  resulting in a decrease of approximately $17,376 in income  from
    net profits interests.

    Gas production decreased approximately 4,200 mcf or 22% during the same
    period, resulting in a decrease of approximately $8,526 in income  from
    net profits interests.

    The  total  decrease in income from net profits interests  due  to  the
    change  in  production  is  approximately  $25,902.   The  decrease  is
    primarily attributable to natural decline.

3.  Lease  operating  costs  and  production  taxes  were  22%  lower,   or
    approximately $33,565 less during the quarter ended June  30,  1998  as
    compared to the quarter ended June 30, 1997.

Costs and Expenses

Total costs and expenses increased to $44,236 from $31,653 for the quarters
ended  June  30,  1998  and 1997, respectively, an increase  of  40%.   The
increase  is  the  result  of  higher depletion  expense  and  general  and
administrative 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
    27%  or approximately $2,583 during the quarter ended June 30, 1998  as
    compared  to the quarter ended June 30, 1997.  Increase in general  and
    administrative costs are the result of higher accounting  fees  due  to
    the  necessity of contracting out preparation of tax depletion and  K-1
    schedules.

2.  Depletion expense increased to $32,000 for the quarter ended  June  30,
    1998  from  $22,000  for the same period in 1997.  This  represents  an
    increase  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.   Contributing
    factors  to  the increase in depletion expense between the  comparative
    periods were the decrease in the price of oil and gas used to determine
    the Partnership's reserves for January 1, 1998 as compared to 1997.

<PAGE>
B.  General  Comparison of the Six Month Periods Ended June  30,  1998  and
    1997

The  following  table  provides certain information  regarding  performance
factors for the six month periods ended June 30, 1998 and 1997:

                                                Six Months
                                                  Ended          Percentage
                                                 June 30,         Increase
                                              1998       1997    (Decrease)
                                              ----       ----    ----------

Average price per barrel of oil          $   11.75      19.56    (40%)
Average price per mcf of gas             $    1.79       2.35    (24%)
Oil production in barrels                   21,900     22,600     (3%)
Gas production in mcf                       33,900     37,800    (10%)
Income from net profits interests        $  50,233    230,393    (78%)
Partnership distributions                $  90,000    356,500    (75%)
Limited partner distributions            $  81,000    320,850    (75%)
Per unit distribution to limited
 partners                                $   13.54      53.63    (75%)
Number of limited partner units              5,983      5,983

Revenues

The  Partnership's income from net profits interests decreased  to  $50,233
from   $230,393  for  the  six  months  ended  June  30,  1998  and   1997,
respectively,  a  decrease  of 78%.  The principal  factors  affecting  the
comparison of the six months ended June 30, 1998 and 1997 are as follows:

1.  The  average  price  for a barrel of oil received  by  the  Partnership
    decreased during the six months ended June 30, 1998 as compared to  the
    six  months ended June 30, 1997 by 40%, or $7.81 per barrel,  resulting
    in  a  decrease  of approximately $176,506 in income from  net  profits
    interests.  Oil sales represented 81% of total oil and gas sales during
    the  six  months ended June 30, 1998 as compared to 83% during the  six
    months ended June 30, 1997.

    The  average  price  for  an  mcf of gas received  by  the  Partnership
    decreased during the same period by 24%, or $.56 per mcf, resulting  in
    a  decrease  of  approximately  $21,168  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
    $197,674.  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 700 barrels or 3% during the six
    months ended June 30, 1998 as compared to the six months ended June 30,
    1997,  resulting in a decrease of approximately $8,225 in  income  from
    net profits interests.

    Gas production decreased approximately 3,900 mcf or 10% during the same
    period, resulting in a decrease of approximately $6,981 in income  from
    net profits interests.

    The  total  decrease in income from net profits interests  due  to  the
    change in production is approximately $15,206.

3.  Lease  operating  costs  and  production  taxes  were  11%  lower,   or
    approximately $32,693 less during the six months ended June 30, 1998 as
    compared to the six months ended June 30, 1997.

Costs and Expenses

Total  costs  and expenses increased to $90,213 from $71,211  for  the  six
months ended June 30, 1998 and 1997, respectively, an increase of 27%.  The
increase is the result of an increase in 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
    16%  or approximately $4,002 during the six months ended June 30,  1998
    as compared to the six months ended June 30, 1997.

2.  Depletion  expense increased to $61,000 for the six months  ended  June
    30, 1998 from $46,000 for the same period in 1997.  This represents  an
    increase  of 33%.  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.   Contributing
    factors  to  the increase in depletion expense between the  comparative
    periods were the decrease in the price of oil and gas 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 $75,500  in
the six months ended June 30, 1998 as compared to approximately $237,000 in
the  six  months ended June 30, 1997.  The primary source of the 1998  cash
flow from operating activities was profitable operations.

Cash  flows  used in financing activities were $90,000 in  the  six  months
ended June 30, 1998 as compared to approximately $356,500 in the six months
ended  June  30,  1997.   The  only use in  financing  activities  was  the
distributions to partners.

Total  distributions during the six months ended June 30, 1998 were $90,000
of  which $81,000 was distributed to the limited partners and $9,000 to the
general partners.  The per unit distribution to limited partners during the
six  months ended June 30, 1998 was $13.54.  Total distributions during the
six  months  ended  June  30,  1997 were $356,500  of  which  $320,850  was
distributed  to  the limited partners and $35,650 to the general  partners.
The  per unit distribution to limited partners during the six months  ended
June 30, 1997 was $53.63.

The  sources  for  the  1998  distributions of $90,000  were  oil  and  gas
operations  of approximately $75,500, with the balance from available  cash
on  hand  at  the  beginning  of  the period.   The  source  for  the  1997
distributions  of  $356,500  was oil and gas  operations  of  approximately
$237,000, with the balance from available cash on hand at the beginning  of
the period.

Since  inception of the Partnership, cumulative monthly cash  distributions
of  $2,547,468  have  been made to the partners.   As  of  June  30,  1998,
$2,304,578 or $385.19 per limited partner unit has been distributed to  the
limited partners, representing a 77% return of the capital contributed.

As  of  June 30, 1998, the Partnership had approximately $57,571 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.

Information Systems for the Year 2000

The  Managing  General Partner provides all data processing  needs  of  the
Partnership.   The Managing General Partner has reviewed and evaluated  its
information  systems  to determine if its systems accurately  process  data
referencing   the   year   2000.   Primarily  all   necessary   programming
modifications  to  correct year 2000 referencing in  the  Managing  General
Partners  internal accounting and operating systems have been made to-date.
However  the  Managing General Partner has not completed its evaluation  of
its vendors and suppliers systems to determine the effect, if any, the non-
compliance  of  such systems would have on the operation  of  the  Managing
General Partnership or the operations 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)                            Reports on Form 8-K:

                  No reports on Form 8-
             K were filed during the quarter ended June 30, 1998.

<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: August 15, 1998

<PAGE>