Page 13 of 14
                                 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 September 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 15.

<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 note 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
nine  month periods ended September 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

                                              September 30,   December 31,
                                                   1998           1997
                                              -------------   ------------
                                               (unaudited)
Assets

Current assets
 Cash and cash equivalents                     $    5,164         20,066
 Receivable from Managing General Partner          20,505        105,891
                                                ---------      ---------
     Total current assets                          25,669        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                   1,776,479      1,703,479
                                                ---------      ---------
     Net oil and gas properties                   468,149        541,149
                                                ---------      ---------
                                               $  493,818        667,106
                                                =========      =========

Liabilities and Partners' Equity

Current liability - Distribution payable       $       21              -
                                                ---------      ---------

Partners' equity
 General partners                                (28,816)       (18,785)
 Limited partners                                 522,613        685,891
                                                ---------      ---------
     Total partners' equity                       493,797        667,106
                                                ---------      ---------
                                               $  493,818        667,106
                                                =========      =========
<PAGE>

          Southwest Royalties Institutional Income Fund X-C, L.P.
                                     
                         Statements of Operations
                                (unaudited)


                                Three Months Ended    Nine Months Ended
                                  September 30,         September 30,
                                  1998      1997        1998      1997
                                  ----      ----        ----      ----
Revenues

Income (loss) from net
 profits interests           $  (11,442)    74,896      38,792   305,289
Interest                             124       500         717     2,858
                                  ------   -------     -------   -------
                                (11,318)    75,396      39,509   308,147
                                  ------   -------     -------   -------
Expenses

General and administrative        11,605     9,097      40,818    34,307
Depreciation, depletion and
 amortization                     12,000    20,000      73,000    66,000
                                  ------   -------     -------   -------
                                  23,605    29,097     113,818   100,307
                                  ------   -------     -------   -------
Net income (loss)            $  (34,923)    46,299    (74,309)   207,840
                                  ======   =======     =======   =======



Net income (loss) allocated to:

 Managing General Partner    $   (2,063)     5,967       (118)    24,646
                                  ======   =======     =======   =======
 General Partner             $     (229)       663        (13)     2,738
                                  ======   =======     =======   =======
 Limited Partners            $  (32,631)    39,669    (74,178)   180,456
                                  ======   =======     =======   =======
  Per limited partner unit   $    (5.45)      6.63      (12.40)    30.16
                                  ======   =======     =======   =======

<PAGE>

          Southwest Royalties Institutional Income Fund X-C, L.P.
                                     
                         Statements of Cash Flows
                                (unaudited)


                                                      Nine Months Ended
                                                        September 30,
                                                       1998       1997
                                                       ----       ----
Cash flows from operating activities

 Cash received from income from net
  profits interests                                $  106,557    348,720
 Cash paid to suppliers                              (23,198)   (34,307)
 Interest received                                        717      2,858
                                                      -------    -------
  Net cash provided by operating activities            84,076    317,271
                                                      -------    -------
Cash flows used in financing activities

 Distributions to partners                           (98,978)  (471,465)
                                                      -------    -------

Net decrease in cash and cash equivalents            (14,902)  (154,194)

 Beginning of period                                   20,066    170,421
                                                      -------    -------
 End of period                                     $    5,164     16,227
                                                      =======    =======

                                                             (continued)
<PAGE>

          Southwest Royalties Institutional Income Fund X-C, L.P.
                                     
                    Statements of Cash Flows, continued
                                (unaudited)


                                                      Nine Months Ended
                                                        September 30,
                                                       1998       1997
                                                       ----       ----
Reconciliation of net income (loss) to net
 cash provided by operating activities

Net income (loss)                                  $ (74,309)    207,840

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

 Depreciation, depletion and amortization              73,000     66,000
 Decrease in receivables                               67,765     43,431
 Increase in payables                                  17,620          -
                                                      -------    -------
Net cash provided by operating activities          $   84,076    317,271
                                                      =======    =======


<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  to  enhance  production.   The  Partnership  could
possibly experience a normal decline in 1998.

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 September 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
three  quarters  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 September 30, 1998 and 1997

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

                                                 Three Months
                                                    Ended        Percentage
                                                September 30,     Increase
                                                1998      1997   (Decrease)
                                                ----      ----   ---------
Average price per barrel of oil            $   10.42     16.87    (38%)
Average price per mcf of gas               $    1.44      2.14    (33%)
Oil production in barrels                      9,400    10,900    (14%)
Gas production in mcf                         14,700    18,300    (20%)
Income (loss) from net profits interests   $(11,422)    74,896   (115%)
Partnership distributions                  $   9,000   115,000    (92%)
Limited partner distributions              $   8,100   103,500    (92%)
Per unit distribution to limited partners  $    1.35     17.30    (92%)
Number of limited partner units                5,983     5,983

Revenues

The  Partnership's income from net profits interests decreased to $(11,442)
from   $74,896  for  the  quarters  ended  September  30,  1998  and  1997,
respectively,  a  decrease of 115%.  The principal  factors  affecting  the
comparison  of  the  quarters ended September 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 September 30, 1998 as compared  to
     the  quarter  ended  September 30, 1997 by 38%, or $6.45  per  barrel,
     resulting  in a decrease of approximately $70,300 in income  from  net
     profits  interests.  Oil sales represented 82% of total  oil  and  gas
     sales during the quarter ended September 30, 1998 and 1997.

     The  average  price  for  an mcf of gas received  by  the  Partnership
     decreased during the same period by 33%, or $.70 per mcf, resulting in
     a  decrease  of  approximately $12,800  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
     $83,100.  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 1,500 barrels or 14% during  the
   quarter  ended  September  30, 1998 as compared  to  the  quarter  ended
   September 30, 1997, resulting in a decrease of approximately $15,600  in
   income from net profits interests.

    Gas production decreased approximately 3,600 mcf or 20% during the same
    period, resulting in a decrease of approximately $5,200 in income  from
    net profits interests.

    The  total  decrease in income from net profits interests  due  to  the
    change  in  production is approximately $20,800.  Decrease  is  due  to
    natural decline.

3.  Lease  operating  costs  and  production  taxes  were  12%  lower,   or
    approximately $17,600 less during the quarter ended September 30,  1998
    as compared to the quarter ended September 30, 1997.

Costs and Expenses

Total costs and expenses decreased to $23,605 from $29,097 for the quarters
ended  September 30, 1998 and 1997, respectively, a decrease of  19%.   The
decrease is the result of lower depletion expense, partially offset  by  an
increase in 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
    28% or approximately $2,500 during the quarter ended September 30, 1998
    as  compared  to the quarter ended September 30, 1997. The increase  in
    general  and administrative costs are due largely to higher  accounting
    fees.   The  10-Q's  are  now  required to be  reviewed  based  on  new
    accounting pronouncements.

2.  Depletion  expense decreased to $12,000 for the quarter ended September
    30,  1998 from $20,000 for the same period in 1997.  This represents  a
    decrease  of 40%.  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  decline in depletion expense between the  comparative
    periods  were the decrease in the price of oil and thus the decline  in
    gross oil and gas revenues.

<PAGE>

B.   General Comparison of the Nine Month Periods Ended September 30,  1998
and 1997

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

                                                 Nine Months
                                                    Ended        Percentage
                                                September 30,     Increase
                                                1998      1997   (Decrease)
                                                ----      ----   ---------
Average price per barrel of oil            $   11.35     18.57   (39%)
Average price per mcf of gas               $    1.68      2.31   (27%)
Oil production in barrels                     31,300    33,700    (7%)
Gas production in mcf                         48,600    55,500   (12%)
Income from net profits interests          $  38,792   305,289   (87%)
Partnership distributions                  $  99,000   471,500   (79%)
Limited partner distributions              $  89,100   424,350   (79%)
Per unit distribution to limited partners  $   14.89     70.93   (79%)
Number of limited partner units                5,983     5,983

Revenues

The  Partnership's income from net profits interests decreased  to  $38,792
from  $305,289  for  the nine months ended September  30,  1998  and  1997,
respectively,  a  decrease  of 87%.  The principal  factors  affecting  the
comparison  of  the nine months ended September 30, 1998 and  1997  are  as
follows:

1.  The  average  price  for a barrel of oil received  by  the  Partnership
    decreased  during the nine months ended September 30, 1998 as  compared
    to  the  nine  months ended September 30, 1997 by  39%,  or  $7.22  per
    barrel,  resulting  in a decrease of approximately $243,300  in  income
    from net profits interests.  Oil sales represented 81% of total oil and
    gas  sales during the nine months ended September 30, 1998 as  compared
    to 83% during the nine months ended September 30, 1997.

    The  average  price  for  an  mcf of gas received  by  the  Partnership
    decreased during the same period by 27%, or $.63 per mcf, resulting  in
    a  decrease  of  approximately  $35,000  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
    $278,300.  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 2,400 barrels or 7% during  the
    nine  months  ended September 30, 1998 as compared to the  nine  months
    ended  September  30,  1997, resulting in a decrease  of  approximately
    $27,200 in income from net profits interests.

    Gas production decreased approximately 6,900 mcf or 12% during the same
    period, resulting in a decrease of approximately $11,600 in income from
    net profits interests.

    The  total  decrease in income from net profits interests  due  to  the
    change in production is approximately $38,800.

3.  Lease  operating  costs  and  production  taxes  were  11%  lower,   or
    approximately  $50,300 less during the nine months ended September  30,
    1998 as compared to the nine months ended September 30, 1997.

Costs and Expenses

Total  costs and expenses increased to $113,818 from $100,307 for the  nine
months ended September 30, 1998 and 1997, respectively, an increase of 13%.
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
    19%  or approximately $6,500 during the nine months ended September 30,
    1998  as  compared to the nine months ended September  30,  1997.   The
    increase in general and administrative costs are due largely to  higher
    accounting fees.  The 10-Q's are now required to be reviewed  based  on
    new accounting pronouncements.

2.  Depletion  expense  increased to $73,000  for  the  nine  months  ended
    September  30,  1998 from $66,000 for the same period  in  1997.   This
    represents an increase of 11%.  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.

<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 $84,100  in
the  nine  months  ended  September 30, 1998 as compared  to  approximately
$317,300  in the nine months ended September 30, 1997.  The primary  source
of the 1998 cash flow from operating activities was profitable operations.

There  were  no  cash flows provided by investing activities  in  the  nine
months ended September 30, 1998 and 1997.

Cash  flows used in financing activities were approximately $98,900 in  the
nine  months ended September 30, 1998 as compared to approximately $471,500
in  the  nine  months ended September 30, 1997.  The only use in  financing
activities was the distributions to partners.

Total  distributions during the nine months ended September 30,  1998  were
$99,000 of which $89,100 was distributed to the limited partners and $9,900
to  the  general  partners.  The per unit distribution to limited  partners
during  the  nine  months  ended September  30,  1998  was  $14.89.   Total
distributions during the nine months ended September 30, 1997 were $471,500
of  which  $424,350 was distributed to the limited partners and $47,150  to
the general partners.  The per unit distribution to limited partners during
the nine months ended September 30, 1997 was $70.93.

The  sources  for  the  1998  distributions of $99,000  were  oil  and  gas
operations  of approximately $84,100, with the balance from available  cash
on  hand  at  the  beginning  o  the  period.   The  source  for  the  1997
distributions  of  $471,500  was oil and gas  operations  of  approximately
$317,300, with the balance from available cash on hand at the beginning  of
the period.

Since  inception of the Partnership, cumulative monthly cash  distributions
of  $2,556,468 have been made to the partners.  As of September  30,  1998,
$2,312,678 or $386.54 per limited partner unit has been distributed to  the
limited partners, representing a 77% return of the capital contributed.

As  of  September  30, 1998, the Partnership had approximately  $25,600  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>


Information Systems for the Year 2000

The  Partnership  relies  on the Managing General Partner  for  their  data
processing  requirements.   This includes use of  a  program  designed  and
implemented  by Midland Southwest Software, the Managing General  Partner's
software subsidiary.  Midland Southwest Software currently has a year  2000
plan  in  effect.   They have surveyed existing programs and  hardware  and
estimate a compliance date of early 1999.  Determination of the total  cost
in connection with the year 2000 compliance issue is difficult to determine
due  to the fact that they are in the process of developing their new  1998
version  of  marketed  oil  and gas software, which  has,  from  inception,
included  year 2000 compliance.  Third party software programs utilized  by
the  Managing General Partner are either in compliance or are not  affected
by  the  year  2000,  with the exception of the payroll service,  which  is
currently modifying its system to accurately handle the Year 2000 issue.

The  Managing  General  Partner has not completed  its  evaluation  of  its
vendors  or  suppliers systems to determine the effect, if  any,  the  non-
compliance  of  such systems would have on the operations of  the  Managing
General  Partner.  Plans are under way to perform an audit in late 1998  or
early  1999  to determine the effect of non-compliance of its  vendors  and
suppliers  on the Managing General Partner and thus formulate a contingency
plan.

A  potential source of risk includes, but is not limited to, the  inability
of  principal  purchasers and suppliers to be year  2000  compliant,  which
could  have a material effect on the Managing General Partner's production,
cash  flow  and overall financial condition, notwithstanding  the  Managing
General  Partner's  actions to prepare its own  information  systems.   The
Managing  General  Partner currently does not have a  contingency  plan  in
place to cover any unforeseen problems encountered that relate to the  year
2000, but intends to produce one before the end of the fiscal year.



<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) 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:     November 15, 1998

<PAGE>