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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, 2004

                                    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 033-47668-03

         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)

                             (432) 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 ___

Indicate  by check mark whether the registrant is an accelerated filer  (as
defined in Exchange Act Rule 12b-2).     Yes     No  X

The  registrant's  outstanding  securities  consist  of  Units  of  limited
partnership  interests for which there exists no established public  market
from which to base a calculation of aggregate market value.


        The total number of pages contained in this report is 24.

<PAGE>
Glossary of Oil and Gas Terms
The  following are abbreviations and definitions of terms commonly used  in
the  oil  and  gas industry that are used in this filing.  All  volumes  of
natural gas referred to herein are stated at the legal pressure base to the
state  or area where the reserves exit and at 60 degrees Fahrenheit and  in
most instances are rounded to the nearest major multiple.

     Bbl. One stock tank barrel, or 42 United States gallons liquid volume.

     Developmental well. A well drilled within the proved area of an oil or
natural gas reservoir to the depth of a stratigraphic horizon known  to  be
productive.

     Exploratory well. A well drilled to find and produce oil or gas in  an
unproved  area to find a new reservoir in a field previously  found  to  be
productive of oil or natural gas in another reservoir or to extend a  known
reservoir.

     Farm-out  arrangement. An agreement whereby the owner of the leasehold
or  working  interest  agrees to assign his interest  in  certain  specific
acreage  to  the assignee, retaining some interest, such as  an  overriding
royalty interest, subject to the drilling of one (1) or more wells or other
performance by the assignee.

     Field. An area consisting of a single reservoir or multiple reservoirs
all  grouped  on  or  related to the same individual geological  structural
feature and/or stratigraphic condition.

     Mcf. One thousand cubic feet.

     Net  Profits  Interest.  An agreement whereby  the  owner  receives  a
specified  percentage of the defined net profits from a producing  property
in  exchange for consideration paid.  The net profits interest  owner  will
not otherwise participate in additional costs and expenses of the property.

     Oil. Crude oil, condensate and natural gas liquids.

     Overriding  royalty  interest. Interests that  are  carved  out  of  a
working  interest, and their duration is limited by the term of  the  lease
under which they are created.

<PAGE>
     Present  value  and  PV-10 Value. When used with respect  to  oil  and
natural gas reserves, the estimated future net revenue to be generated from
the  production of proved reserves, determined in all material respects  in
accordance  with  the  rules and regulations of the  SEC  (generally  using
prices  and costs in effect as of the date indicated) without giving effect
to  non-property  related  expenses  such  as  general  and  administrative
expenses,  debt service and future income tax expenses or to  depreciation,
depletion  and  amortization, discounted using an annual discount  rate  of
10%.

     Production  costs.  Costs incurred to operate and maintain  wells  and
related  equipment  and facilities, including depreciation  and  applicable
operating  costs  of support equipment and facilities and  other  costs  of
operating and maintaining those wells and related equipment and facilities.

     Proved Area. The part of a property to which proved reserves have been
specifically attributed.

     Proved  developed oil and gas reserves. Proved developed oil  and  gas
reserves  are  reserves that can be expected to be recovered from  existing
wells with existing equipment and operating methods.

     Proved properties. Properties with proved reserves.

     Proved  reserves. The estimated quantities of crude oil, natural  gas,
and  natural  gas liquids that geological and engineering data  demonstrate
with  reasonable  certainty to be recoverable in future  years  from  known
reservoirs under existing economic and operating conditions.

     Proved  undeveloped reserves. Proved undeveloped oil and gas  reserves
are  reserves that are expected to be recovered from new wells on undrilled
acreage,  or  from existing wells where a relatively major  expenditure  is
required for recompletion.

     Reservoir.  A porous and permeable underground formation containing  a
natural  accumulation  of  producible  oil  or  gas  that  is  confined  by
impermeable  rock  or water barriers and is individual  and  separate  from
other reservoirs.

     Royalty  interest.  An  interest in an oil and  natural  gas  property
entitling  the  owner to a share of oil or natural gas production  free  of
costs of production.

     Working  interest.  The operating interest that gives  the  owner  the
right  to  drill, produce and conduct operating activities on the  property
and a share of production.

     Workover.  Operations  on  a producing well  to  restore  or  increase
production.

<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, 2003, which are found in the Registrant's Form
10-K  Report  for  2003 filed with the Securities and Exchange  Commission.
The December 31, 2003 balance sheet included herein has been taken from the
Registrant's  2003 Form 10-K Report.  Operating results for the  three  and
six month periods ended June 30, 2004 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,
                                   2004      2003
                                   ----      ----
                                 (unaudit
                                   ed)
Assets
----------

Current assets:
 Cash and cash equivalents    $  32,929    26,631
  Receivable  from  Managing     92,654    40,531
General Partner
                                 --------  --------
                                 ----      ----
   Total current assets          125,583   67,162
                                 --------  --------
                                 ----      ----
Oil  and  gas  properties  -
using the full-
 method of accounting            2,395,60  2,395,60
                                 1         1
       Less      accumulated
depreciation,
         depletion       and     2,234,14  2,228,14
amortization                     4         3
                                 --------  --------
                                 ----      ----
      Net   oil   and    gas     161,457   167,458
properties
                                 --------  --------
                                 ----      ----
                              $  287,040   234,620
                                 =======   =======
Liabilities  and   Partners'
Equity
----------------------------
-----------
Current liability:
 Distribution payable         $  101       -
                                 --------  --------
                                 ----      ----

Asset retirement obligation      770,479   740,845
                                 --------  --------
                                 ----      ----

Partners' equity:
 General partners                (89,586)  (92,455)
 Limited partners                (393,954  (413,770
                                 )         )
                                 --------  --------
                                 ----      ----
   Total partners' equity        (483,540  (506,225
                                 )         )
                                 --------  --------
                                 ----      ----
                              $  287,040   234,620
                                 =======   =======

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

                                   Three Months Ended   Six Months Ended
                                        June 30,            June 30,
                                     2004      2003      2004      2003
                                    -----     -----     -----     -----
Revenues
-------------
Income    from   net   profits  $  68,364    26,207    159,588   91,857
interests
Interest                           59        94        102       146
Other                              -         -         250       -
                                   --------  --------  --------  --------
                                   --        --        --        --
                                   68,423    26,301    159,940   92,003
                                   --------  --------  --------  --------
                                   --        --        --        --
Expenses
-------------
General and administrative         14,596    17,082    27,165    27,317
Depreciation,  depletion   and     3,000     9,000     6,000     21,000
amortization
Accretion  of asset retirement     14,817    16,150    29,634    32,420
obligation
                                   --------  --------  --------  --------
                                   --        --        --        --
                                   32,413    42,232    62,799    80,737
                                   --------  --------  --------  --------
                                   --        --        --        --
Net    income   (loss)    from     36,010    (15,931)  97,141    11,266
continuing operations

Results    from   discontinued
operations-
  sale of oil and gas lease  -     149       (94)      (4,456)   14,438
See Note 4
                                   --------  --------  --------  --------
                                   --        --        --        -
Net   income   (loss)   before     36,159    (16,025)  92,685    25,704
cumulative effect

Cumulative effect of change in
accounting
  principle - SFAS No.  143  -     -         -         -         (599,030
See Note 3                                                       )
                                   --------  --------  --------  --------
                                   --        --        --        --
Net income (loss)               $  36,159    (16,025)  92,685    (573,326
                                                                 )
                                   ======    ======    ======    ======
Net  income  (loss)  allocated
to:
 Managing General Partner       $  3,524     (542)     8,882     (49,529)
                                   ======    ======    ======    ======
 General Partner                $  392       (60)      987       (5,504)
                                   ======    ======    ======    ======
 Limited Partners               $  32,243    (15,423)  82,816    (518,293
                                                                 )
                                   ======    ======    ======    ======
   Per  limited  partner  unit
before discontinued
    operations and  cumulative  $     5.37    (2.55)     14.51
effect                                                           1.34
   Discontinued operations per         .02    (.03)      (.67)      2.14
limited partner unit
     Cumulative   effect   per     -         -         -         (90.11)
limited partner unit
                                   --------  --------  --------  --------
                                   --        --        --        --
  Per limited partner unit      $     5.39    (2.58)     13.84   (86.63)
                                   ======    ======    ======    ======

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

                                       Six Months Ended
                                           June 30,
                                        2004      2003
                                       -----     -----

Cash    flows   from    operating
activities:

  Cash received from income  from  $  104,759   95,168
net profits interests
 Cash paid to suppliers               (24,458)  (17,679)
  Cash received from discontinued     (4,456)   16,438
operations
 Interest received                    102       146
 Other                                250       -
                                      --------  --------
                                      --        --
   Net cash provided by operating     76,197    94,073
activities
                                      --------  --------
                                      --        --
Cash  flows provided by investing
activities:
 Sales of oil and gas properties      -         51,200
                                      --------  --------
                                      --        --
Cash   flows  used  in  financing
activities:
 Distributions to partners            (69,899)  (125,000
                                                )
                                      --------  --------
                                      --        --
Net  increase  in cash  and  cash     6,298     20,273
equivalents

 Beginning of period                  26,631    20,887
                                      --------  --------
                                      --        --
 End of period                     $  32,929    41,160
                                      ======    ======
Reconciliation  of   net   income
(loss) to net
   cash  provided  by  (used  in)
operating activities:

Net income (loss)                  $  92,685    (573,326
                                                )

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

   Depreciation,  depletion   and     6,000     21,000
amortization
  Accretion  of asset  retirement     29,634    32,420
obligation
  Cumulative effect of change  in
accounting
  principle - SFAS No. 143            -         599,030
     (Increase)    decrease    in     (54,829)  3,311
receivables
 Increase in payables                 2,707     11,638
                                      --------  --------
                                      --        --
Net  cash  provided by  operating  $  76,197    94,073
activities
                                      ======    ======
Noncash  investing and  financing
activities:
   Increase   in  oil   and   gas
properties - Adoption
  of SFAS No.143                   $  -         214,465
                                      ======    ======
   Decrease   in  oil   and   gas
properties - SFAS No. 143
  sale of property                 $            6,114
                                      ======    ======
<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.  a
     wholly-owned  subsidiary of Clayton Williams Energy, Inc.,  serves  as
     the Managing General Partner and H. H. Wommack, III, as the individual
     general  partner.   Effective  April 1, 2004,  Mr.  Wommack  sold  his
     general  partner interest to the Managing General Partner.   Revenues,
     costs and expenses are allocated as follows:

                              Limited   General
                              Partners  Partners
                              --------  --------
Interest  income on  capital  100%      -
contributions
Oil and gas sales             90%       10%
All other revenues            90%       10%
Organization  and   offering  100%      -
costs (1)
Syndication costs             100%      -
Amortization of organization  100%      -
costs
Property acquisition costs    100%      -
Gain/loss    on     property  90%       10%
disposition
Operating and administrative  90%       10%
costs (2)
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 June 30, 2004, and  for  the
     three  and  six  months  ended June 30, 2004, 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 Partnership's Annual
     Report on Form 10-K for the year ended December 31, 2003.


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

                      Notes to Financial Statements

3.   Cumulative effect of change in accounting principle - SFAS No. 143
     On  January  1, 2003, the Partnership adopted Statement  of  Financial
     Accounting   Standards  No.  143,  Accounting  for  Asset   Retirement
     Obligations  ("SFAS No. 143").  Adoption of SFAS No. 143  is  required
     for  all  companies with fiscal years beginning after June  15,  2002.
     The new standard requires the Partnership to recognize a liability for
     the  present  value  of  all  legal obligations  associated  with  the
     retirement  of tangible long-lived assets and to capitalize  an  equal
     amount as a cost of the asset and depreciate the additional cost  over
     the  estimated  useful  life of the asset.  On January  1,  2003,  the
     Partnership    recorded   additional   costs,   net   of   accumulated
     depreciation,  of  approximately $214,465, a long  term  liability  of
     approximately  $813,495 and a loss of approximately $599,030  for  the
     cumulative  effect  on  depreciation  of  the  additional  costs   and
     accretion  expense  on  the liability related to expected  abandonment
     costs  of  its oil and natural gas producing properties.  At June  30,
     2004,  the  asset retirement obligation was $770,479. The increase  in
     the  balance  from  January 1, 2004 is due  to  accretion  expense  of
     $29,634.

4.   Discontinued Operations - Sale of oil and gas leases
     During 2003, the Partnership sold its interest in certain oil and  gas
     wells  for  $81,184  sales  proceeds and  retired  $100,007  of  asset
     retirement  obligation  associated with  the  properties.   Since  the
     Partnership  is  under the full cost pool method  of  accounting,  the
     sales  proceeds and asset retirement obligation liability  were  taken
     against  the  oil and gas properties asset account and  therefore,  no
     gain or loss was recorded and shown on the statement of operations  as
     part  of  the  discontinued operations. Operating  expenses  for  2004
     represent  plugging  and abandonment costs that  the  Partnership  was
     contractually committed to perform prior to the sale of the  property.
     Plugging  and abandonment services were performed during  the  quarter
     ended  March 31, 2004.  Pursuant to the requirements of SFAS No.  144,
     the  operating  results from these properties have  been  reported  as
     discontinued operations in the accompanying statements of operations.

     The   following   table   summarizes  certain   historical   operating
     information related to the discontinued operations:

                        Three months ended      Six months ended
                             June 30,               June 30,
                         2004       2003         2004      2003
Income (loss) from net
profit
   interest             $ 149     (94)        (4,456)    14,438

5.   Change in Control of Managing General Partner
     On  May  21,  2004,  Clayton Williams Energy, Inc.  acquired  all  the
     outstanding common stock of Southwest Royalties Inc. through a merger.
     Clayton  Williams  Energy,  Inc. paid  $57.1  million  to  holders  of
     Southwest  Royalties,  Inc.  common stock and  common  stock  warrants
     ($45.01   per   share)   and  assumed  and  refinanced   approximately
     $113.9 million of assumed bank debt at closing.


<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.  The  economic
life  of  the  Partnership  thus  depends on  the  period  over  which  the
Partnership's oil and gas reserves are economically recoverable.

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.

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
sold.

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, 2004, the net capitalized costs  did  not
exceed the estimated present value of oil and gas reserves.
..

<PAGE>
The  Partnership's  interest  in oil and gas  properties  consists  of  net
profits  interests  in  proved properties located  within  the  continental
United  States.   A net profits interest is created when  the  owner  of  a
working  interest in a property enters into an arrangement  providing  that
the  net profits interest owner will receive a stated percentage of the net
profit  from  the  property.   The  net profits  interest  owner  will  not
otherwise participate in additional costs and expenses of the property.

The  Partnership recognizes income from its net profits interest in oil and
gas property on an accrual basis, while the quarterly cash distributions of
the net profits interest are based on a calculation of actual cash received
from  oil  and  gas sales, net of expenses incurred during  that  quarterly
period.   If  the  net  profits interest calculation  results  in  expenses
incurred  exceeding the oil and gas income received during  a  quarter,  no
cash  distribution is due to the Partnership's net profits  interest  until
the  deficit is recovered from future net profits.  The Partnership accrues
a quarterly loss on its net profits interest provided there is a cumulative
net  amount  due for accrued revenue as of the balance sheet date.   As  of
June  30,  2004,  there were no timing differences,  which  resulted  in  a
deficit net profit interest.

Critical Accounting Policies

The  Partnership follows the full cost method of accounting for its oil and
gas  properties.   The  full cost method subjects  companies  to  quarterly
calculations of a "ceiling", or limitation on the amount of properties that
can  be capitalized on the balance sheet.  If the Partnership's capitalized
costs  are in excess of the calculated ceiling, the excess must be  written
off as an expense.

The  Partnership's discounted present value of its proved oil  and  natural
gas  reserves  is  a  major  component  of  the  ceiling  calculation,  and
represents  the  component  that requires the  most  subjective  judgments.
Estimates  of  reserves are forecasts based on engineering data,  projected
future  rates  of  production and the timing of future  expenditures.   The
process  of  estimating oil and natural gas reserves  requires  substantial
judgment,  resulting  in  imprecise determinations,  particularly  for  new
discoveries.   Different reserve engineers may make different estimates  of
reserve  quantities  based  on the same data.   The  Partnership's  reserve
estimates are prepared by outside consultants.  Quarterly reserve estimates
are prepared by the Managing General Partner's internal staff of engineers.

The  passage  of  time  provides  more  qualitative  information  regarding
estimates of reserves, and revisions are made to prior estimates to reflect
updated  information.   However,  there  can  be  no  assurance  that  more
significant  revisions  will not be necessary in  the  future.   If  future
significant  revisions  are  necessary  that  reduce  previously  estimated
reserve quantities, it could result in a full cost property writedown.   In
addition to the impact of these estimates of proved reserves on calculation
of  the  ceiling,  estimates  of proved reserves  are  also  a  significant
component of the calculation of DD&A.

While  the quantities of proved reserves require substantial judgment,  the
associated prices of oil and natural gas reserves that are included in  the
discounted  present  value of the reserves do not  require  judgment.   The
ceiling calculation dictates that prices and costs in effect as of the last
day  of  the  period are generally held constant indefinitely. Because  the
ceiling  calculation dictates that prices in effect as of the last  day  of
the  applicable quarter are held constant indefinitely, the resulting value
is  not indicative of the true fair value of the reserves.  Oil and natural
gas  prices have historically been cyclical and, on any particular  day  at
the  end of a quarter, can be either substantially higher or lower than the
Partnership's  long-term price forecast that is a barometer for  true  fair
value.


<PAGE>
Results of Operations

A.  General Comparison of the Quarters Ended June 30, 2004 and 2003

The  following  table  provides certain information  regarding  performance
factors for the quarters ended June 30, 2004 and 2003:

                                    Three Months
                                       Ended         Percenta
                                                        ge
                                      June 30,       Increase
                                   2004      2003    (Decreas
                                                        e)
                                   ----      ----    --------
                                                        --
Average price per barrel  of  $   34.79              36%
oil                                        25.54
Average price per mcf of gas  $    4.58              12%
                                           4.10
Oil production in barrels        5,820     5,880     (1%)
Gas production in mcf            5,750     4,912     17%
Income   from  net   profits  $  68,364    26,207    161%
interests
Partnership distributions     $  40,000    75,000    47%
Limited              partner  $  36,000    67,500    47%
distributions
Per  unit  distribution   to
limited
 partners                     $    6.02              47%
                                           11.28
Number  of  limited  partner     5,983     5,983
units

Revenues

The  Partnership's income from net profits interests increased  to  $68,364
from  $26,207  for the quarters ended June 30, 2004 and 2003, respectively,
an increase of 161%.  The principal factors affecting the comparison of the
quarters ended June 30, 2004 and 2003 are as follows:

1.  The  average  price  for a barrel of oil received  by  the  Partnership
    increased  during the quarter ended June 30, 2004 as  compared  to  the
    quarter  ended June 30, 2003 by 36%, or $9.25 per barrel, resulting  in
    an  increase  of  approximately $53,800  in  income  from  net  profits
    interests.  Oil sales represented 88% of total oil and gas sales during
    the  quarters ended June 30, 2004 as compared to 88% during the quarter
    ended June 30, 2003.

    The  average  price  for  an  mcf of gas received  by  the  Partnership
    increased during the same period by 12%, or $.48 per mcf, resulting  in
    an  increase  of  approximately  $2,800  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
    $56,600.   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 60 barrels or  1%  during  the
    quarter  ended June 30, 2004 as compared to the quarter ended June  30,
    2003,  resulting in a decrease of approximately $1,500 in  income  from
    net profits interests.

    Gas  production increased approximately 838 mcf or 17% during the  same
    period, resulting in an increase of approximately $3,400 in income from
    net profits interests.

    The  net total increase in income from net profits interests due to the
    change  in  production is approximately $1,900.  The  increase  in  gas
    volumes is from improved performance on two producing properties.

3.  Lease  operating  costs  and  production  taxes  were  11%  higher,  or
    approximately $16,400 more during the quarter ended June  30,  2004  as
    compared  to  the  quarter  ended June  30,  2003.   The  higher  lease
    operating  costs are from well and surface repair work on the injection
    system of a producing property.

Costs and Expenses

Total costs and expenses decreased to $32,413 from $42,232 for the quarters
ended  June  30,  2004  and 2003, respectively, a  decrease  of  23%.   The
decrease  is  the  result of lower general and administrative  expense  and
depletion expense and accretion 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
    15%  or approximately $2,500 during the quarter ended June 30, 2004  as
    compared  to  the quarter ended June 30, 2003. The higher  general  and
    administrative expense in 2003 is due to legal fees associated with the
    amendments to the Partnership's December 31, 2002 Annual Report on Form
    10-K and March 31, 2003 Quarterly Report on Form 10-Q.

2.  Depletion  expense decreased to $3,000 for the quarter ended  June  30,
    2004  from  $9,000  for  the same period in 2003.   This  represents  a
    decrease  of 67%.  The contributing factor to the decrease in depletion
    expense is in relation to the BOE depletion rate for the quarter  ended
    June 30, 2004, which was $.44 applied to 6,778 BOE as compared to $1.35
    applied to 6,486 BOE for the same period in 2003.

3.  Accretion expense decreased to $14,817 for the quarter ended  June  30,
    2004  from  $16,150  for the same period in 2003.   This  represents  a
    decrease of 8%.

<PAGE>
B.  General  Comparison of the Six Month Periods Ended June  30,  2004  and
    2003

The  following  table  provides certain information  regarding  performance
factors for the six month periods ended June 30, 2004 and 2003:

                                     Six Months
                                       Ended         Percenta
                                                        ge
                                      June 30,       Increase
                                   2004      2003    (Decreas
                                                        e)
                                   ----      ----    --------
                                                        --
Average price per barrel  of  $    32.93             16%
oil                                        28.41
Average price per mcf of gas  $     4.57             9%
                                           4.20
Oil production in barrels        11,530    12,274    (6%)
Gas production in mcf            11,550    9,110     27%
Income   from  net   profits  $  159,588   91,857    74%
interests
Partnership distributions     $  70,000    125,000   (44%)
Limited              partner  $  63,000    112,500   (44%)
distributions
Per  unit  distribution   to
limited
 partners                     $    10.53             (44%)
                                           18.80
Number  of  limited  partner     5,983     5,983
units

Revenues

The  Partnership's income from net profits interests increased to  $159,588
from $91,857 for the six months ended June 30, 2004 and 2003, respectively,
an  increase of 74%.  The principal factors affecting the comparison of the
six months ended June 30, 2004 and 2003 are as follows:

1.  The  average  price  for a barrel of oil received  by  the  Partnership
    increased during the six months ended June 30, 2004 as compared to  the
    six  months ended June 30, 2003 by 16%, or $4.51 per barrel,  resulting
    in  an  increase  of approximately $52,000 in income from  net  profits
    interests.  Oil sales represented 88% of total oil and gas sales during
    the  six  months ended June 30, 2004 as compared to 90% during the  six
    months ended June 30, 2003.

    The  average  price  for  an  mcf of gas received  by  the  Partnership
    increased  during the same period by 9%, or $.37 per mcf, resulting  in
    an  increase  of  approximately  $4,300  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
    $56,300.  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 744 barrels or 6% during the six
    months ended June 30, 2004 as compared to the six months ended June 30,
    2003,  resulting in a decrease of approximately $21,100 in income  from
    net profits interests.

    Gas production increased approximately 2,440 mcf or 27% during the same
    period,  resulting  in an increase of approximately $10,300  in  income
    from net profits interests.

    The  total  decrease in income from net profits interests  due  to  the
    change  in  production is approximately $10,800.  The increase  in  gas
    volumes is from improved performance on two producing properties.

3.  Lease   operating  costs  and  production  taxes  were  8%  lower,   or
    approximately $22,300 less during the six months ended June 30, 2004 as
    compared to the six months ended June 30, 2003.

Costs and Expenses

Total  costs  and expenses decreased to $62,799 from $80,737  for  the  six
months ended June 30, 2004 and 2003, respectively, a decrease of 22%.   The
decrease  is  the  result  of  lower general  and  administrative  expense,
depletion expense and accretion 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 1%
    or  approximately  $200 during the six months ended June  30,  2004  as
    compared to the six months ended June 30, 2003.  The higher general and
    administrative expense in 2003 is due to legal fees associated with the
    amendments to the Partnership's December 31, 2002 Annual Report on Form
    10-K and March 31, 2003 Quarterly Report on Form 10-Q.

2.  Depletion expense decreased to $6,000 for the six months ended June 30,
    2004  from  $21,000  for the same period in 2003.   This  represents  a
    decrease  of 71%.  The contributing factor to the decrease in depletion
    expense  is  in relation to the BOE depletion rate for the  six  months
    ended  June 30, 2004, which was $.45 applied to 13,455 BOE as  compared
    to $1.52 applied to 13,792 BOE for the same period in 2003.

3.  Accretion  expense decreased to $29,634 for the six months  ended  June
    30,  2004 from $32,420 for the same period in 2003.  This represents  a
    decrease of 9%.


<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
$76,200  in the six months ended June 30, 2004 as compared to approximately
$94,100 in the six months ended June 30, 2003.

There  were  no cash flows used in investing activities in the  six  months
ended  June 2004.  Cash flows provided by investing activities in  the  six
months ended June 30, 2003 were approximately $51,200.

Cash  flows used in financing activities were approximately $69,900 in  the
six months ended June 30, 2004 as compared to approximately $125,000 in the
six   months  ended  .  The  only  use  in  financing  activities  was  the
distributions to partners.

Total  distributions during the six months ended June 30, 2004 were $70,000
of  which $63,000 was distributed to the limited partners and $7,000 to the
general partners.  The per unit distribution to limited partners during the
six  months ended June 30, 2004 was $10.53.  Total distributions during the
six  months  ended  June  30,  2003 were $125,000  of  which  $112,500  was
distributed  to  the limited partners and $12,500 to the general  partners.
The  per unit distribution to limited partners during the six months  ended
June 30, 2003 was $18.80.

The  sources  for  the  2004  distributions of $70,000  were  oil  and  gas
operations  of  approximately  $76,200,  resulting  in  excess   cash   for
contingencies  or  subsequent distributions.   The  sources  for  the  2003
distributions  of  $125,000  were oil and gas operations  of  approximately
$94,100  and the change in oil and gas properties of approximately $51,200,
resulting in excess cash for contingencies or subsequent distributions.

Cumulative cash distributions of $3,517,839 have been made to the partners.
As  of  June 30, 2004, $3,183,875 or $532.15 per limited partner  unit  has
been distributed to the limited partners, representing a 100% return of the
capital and a 6% return on capital contributed.

As  of June 30, 2004, the Partnership had approximately $125,500 in working
capital.   The  Managing  General Partner knows of no  unusual  contractual
commitments.   Although the partnership held many long-lived properties  at
inception,  because of the restrictions on property development imposed  by
the partnership agreement, the Partnership cannot develop its non-producing
properties, if any.  Without continued development, the producing  reserves
continue  to  deplete.  Accordingly, as the Partnership's  properties  have
matured  and  depleted,  the  net  cash  flows  from  operations  for   the
partnership  has  steadily  declined, except in  periods  of  substantially
increased  commodity pricing.  Maintenance of properties and administrative
expenses for the Partnership are increasing relative to production.  As the
properties   continue   to   deplete,   maintenance   of   properties   and
administrative costs as a percentage of production are expected to continue
to increase.

The  partnership  intends to fund its asset retirement obligations  in  the
future  from cash flow from operations or, to the extent possible,  through
the  sale  of  properties  and  the related  transfer  of  the  abandonment
obligations to the purchasers.  Significant decreases in future oil and gas
commodity prices or currently projected production volumes would impair the
Partnership's ability to fund the asset retirement obligations through cash
flow from operations.

<PAGE>
Managing General Partner

On May 21, 2004, Clayton Williams Energy, Inc. acquired all the outstanding
common  stock  of  Southwest  Royalties Inc.  through  a  merger.   Clayton
Williams Energy, Inc. paid $57.1 million to holders of Southwest Royalties,
Inc.  common stock and common stock warrants ($45.01 per share) and assumed
and  refinanced  approximately  $113.9 million  of  assumed  bank  debt  at
closing.   In connection with the transaction, Blue Heel Company, a  wholly
owned subsidiary of Southwest Royalties, Inc., acquired the general partner
interest from H.H. Wommack, III.

Recent Accounting Pronouncements

The  EITF is considering two issues related to the reporting of oil and gas
mineral  rights.  Issue No. 03-O, "Whether Mineral Rights Are  Tangible  or
Intangible Assets," is whether or not mineral rights are intangible  assets
pursuant  to  SFAS  No.  141,  "Business  Combinations."  Issue  No.  03-S,
"Application of SFAS No. 142, Goodwill and Other Intangible Assets, to  Oil
and  Gas  Companies,"  is, if oil and gas drilling  rights  are  intangible
assets,  whether  those  assets  are  subject  to  the  classification  and
disclosure provisions of SFAS No. 142.  The Partnership classifies the cost
of oil and gas mineral rights as properties and equipment and believes that
this is consistent with oil and gas accounting and industry practice.   The
staff  of the FASB has issued a proposed position clarifying that SFAS  No.
142  does not supersede the balance sheet classification and disclosure for
drilling  and mineral rights of oil and gas producing entities  within  the
scope  of FASB No. 19.   If SFAS No. 142 is determined to apply to oil  and
gas   companies,   the  Partnership  may  be  required  to   make   certain
reclassifications within property and equipment on the balance  sheet,  and
additional  disclosures may be required.  There would be no effect  on  the
statement of income or cash flows as the intangible assets related  to  oil
and  gas mineral rights would continue to be amortized under the full  cost
method of accounting.


<PAGE>
Item 3.   Quantitative and Qualitative Disclosures About Market Risk

The Partnership is not a party to any derivative or
embedded derivative instruments.

Item 4.   Controls and Procedures

Disclosure Controls and Procedures
As  of  the  six months ended June 30, 2004, L. Paul Latham, President  and
Chief  Executive Officer of the Managing General Partner, and Mel G. Riggs,
Vice President and Chief Financial Officer of the Managing General Partner,
evaluated  the effectiveness of the Partnership's disclosure  controls  and
procedures.  Based on their evaluation, they believe that:

     The  disclosure  controls  and  procedures  of  the  Partnership  were
     effective in ensuring that information required to be disclosed by the
     Partnership in the reports it files or submits under the Exchange  Act
     was  recorded,  processed,  summarized and reported  within  the  time
     periods specified in the SEC's rules and forms; and

     The  disclosure  controls  and  procedures  of  the  Partnership  were
     effective  in  ensuring  that  material  information  required  to  be
     disclosed by the Partnership in the report it filed or submitted under
     the  Exchange  Act was accumulated and communicated  to  the  Managing
     General  Partner's  management, including its Chief Executive  Officer
     and  Chief Financial Officer, as appropriate to allow timely decisions
     regarding required disclosure.

Internal Control Over Financial Reporting
There  has  not been any change in the Partnership's internal control  over
financial reporting that occurred during the six months ended June 30, 2004
that has materially affected, or is reasonably likely to materially affect,
internal control over financial reporting.


<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:

               31.1 Rule 13a-14(a)/15d-14(a) Certification
31.2 Rule 13a-14(a)/15d-14(a) Certification
               32.1 Certification of Chief Executive Officer
Pursuant to 18 U.S.C. Section
                  1350, as
                  adopted  Pursuant  to Section 906 of  the  Sarbanes-Oxley
                  Act of 2002
               32.2 Certification of Chief Financial Officer
Pursuant to 18 U.S.C. Section
                  1350, as
                  adopted Pursuant to Section 906 of the Sarbanes-Oxley Act
               of 2002


        (b)  Reports on Form 8-K:

                 The Partnership filed an 8-K on June 3, 2004 under Item  1
               "Changes  in  Control of Registrant" and Item  7  "Financial
               Statements, Pro forma Financial Information and Exhibits."

<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/ Mel G. Riggs
                                   Mel G. Riggs
                                     Vice  President  and  Chief  Financial
Officer


Date:  August 12, 2004



<PAGE>



                    SECTION 302 CERTIFICATION                Exhibit 31.1


I, L. Paul Latham, certify that:

1.    I  have  reviewed  this quarterly report on Form  10-Q  of  Southwest
Royalties Institutional Income Fund X-C, L.P.

2.Based  on my knowledge, this report does not contain any untrue statement
  of  a  material fact or omit to state a material fact necessary  to  make
  the  statements  made,  in light of the circumstances  under  which  such
  statements  were made, not misleading with respect to the period  covered
  by this report;

3.Based  on  my  knowledge, the financial statements, and  other  financial
  information  included  in  this report, fairly present  in  all  material
  respects  the financial condition, results of operations and  cash  flows
  of the registrant as of, and for, the periods presented in this report;

4.The  registrant's other certifying officer(s) and I are  responsible  for
  establishing  and  maintaining disclosure  controls  and  procedures  (as
  defined   in  Exchange  Act  Rules  13a-15(e)  and  15d-15(e))  for   the
  registrant and have:

  a)Designed  such  disclosure  controls and  procedures,  or  caused  such
     disclosure   controls  and  procedures  to  be  designed   under   our
     supervision,  to  ensure  that material information  relating  to  the
     registrant, including its consolidated subsidiaries, is made known  to
     us  by others within those entities, particularly during the period in
     which this report is being prepared;

  b)Evaluated  the  effectiveness of the registrant's  disclosure  controls
     and  procedures and presented in this report our conclusions about the
     effectiveness of the disclosure controls and procedures, as of the end
     of the period covered by this report based on such evaluation; and

  c)Disclosed  in  this  report  any change in  the  registrant's  internal
     control over financial reporting that occurred during the registrant's
     most recent fiscal quarter (the registrant's fourth fiscal quarter  in
     the  case  of  an annual report) that has materially affected,  or  is
     reasonably  likely  to  materially affect, the  registrant's  internal
     control over financial reporting; and

5.The  registrant's other certifying officer(s) and I have disclosed, based
  on  our  most  recent  evaluation  of  internal  control  over  financial
  reporting,  to  the  registrant's auditors and  the  audit  committee  of
  registrant's  board  of directors (or persons performing  the  equivalent
  functions):

  a)All  significant deficiencies and material weaknesses in the design  or
     operation   of   internal  control  over  financial  reporting   which
     reasonably  likely  to  adversely affect the registrant's  ability  to
     record, process, summarize and report financial information; and

  b)Any  fraud, whether or not material, that involves management or  other
     employees  who  have  a significant role in the registrant's  internal
     control over financial reporting.


Date:  August 12, 2004             /s/ L. Paul Latham
                                   L. Paul Latham
                                   President and Chief Executive Officer
                                   of Southwest Royalties, Inc., the
                                   Managing General Partner of
                                   Southwest Royalties Institutional Income
Fund X-C, L.P.



<PAGE>
                    SECTION 302 CERTIFICATION                Exhibit 31.2


I, Mel G. Riggs, certify that:

1.    I  have  reviewed  this quarterly report on Form  10-Q  of  Southwest
Royalties Institutional Income Fund X-C, L.P.

2.Based  on my knowledge, this report does not contain any untrue statement
  of  a  material fact or omit to state a material fact necessary  to  make
  the  statements  made,  in light of the circumstances  under  which  such
  statements  were made, not misleading with respect to the period  covered
  by this report;

3.Based  on  my  knowledge, the financial statements, and  other  financial
  information  included  in  this report, fairly present  in  all  material
  respects  the financial condition, results of operations and  cash  flows
  of the registrant as of, and for, the periods presented in this report;

4.The  registrant's other certifying officer(s) and I are  responsible  for
  establishing  and  maintaining disclosure  controls  and  procedures  (as
  defined   in  Exchange  Act  Rules  13a-15(e)  and  15d-15(e))  for   the
  registrant and have:

  a)Designed  such  disclosure  controls and  procedures,  or  caused  such
     disclosure   controls  and  procedures  to  be  designed   under   our
     supervision,  to  ensure  that material information  relating  to  the
     registrant, including its consolidated subsidiaries, is made known  to
     us  by others within those entities, particularly during the period in
     which this report is being prepared;

  b)Evaluated  the  effectiveness of the registrant's  disclosure  controls
     and  procedures and presented in this report our conclusions about the
     effectiveness of the disclosure controls and procedures, as of the end
     of the period covered by this report based on such evaluation; and

  c)Disclosed  in  this  report  any change in  the  registrant's  internal
     control over financial reporting that occurred during the registrant's
     most recent fiscal quarter (the registrant's fourth fiscal quarter  in
     the  case  of  an annual report) that has materially affected,  or  is
     reasonably  likely  to  materially affect, the  registrant's  internal
     control over financial reporting; and

5.The  registrant's other certifying officer(s) and I have disclosed, based
  on  our  most  recent  evaluation  of  internal  control  over  financial
  reporting,  to  the  registrant's auditors and  the  audit  committee  of
  registrant's  board  of directors (or persons performing  the  equivalent
  functions):

  a)All  significant deficiencies and material weaknesses in the design  or
     operation   of   internal  control  over  financial  reporting   which
     reasonably  likely  to  adversely affect the registrant's  ability  to
     record, process, summarize and report financial information; and

  b)Any  fraud, whether or not material, that involves management or  other
     employees  who  have  a significant role in the registrant's  internal
     control over financial reporting.


Date:  August 12, 2004             /s/ Mel G. Riggs
                                   Mel G. Riggs
                                     Vice  President  and  Chief  Financial
Officer of
                                   Southwest Royalties, Inc., the
                                   Managing General Partner of
                                   Southwest Royalties Institutional Income
Fund X-C, L.P.


<PAGE>
                     CERTIFICATION PURSUANT TO             Exhibit
                                   32.1
                          19 U.S.C. SECTION 1350,
                          AS ADOPTED PURSUANT TO
               SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002


      In  connection  with  the  Quarterly Report  of  Southwest  Royalties
Institutional Income Fund X-C, Limited Partnership (the "Company") on  Form
10-Q  for the period ending June 30, 2004 as filed with the Securities  and
Exchange  Commission on the date hereof (the "Report"), I, L. Paul  Latham,
Chief  Executive  Officer of the Managing General Partner of  the  Company,
certify,  pursuant to 18 U.S.C.  1350, as adopted pursuant to  906  of  the
Sarbanes-Oxley Act of 2002, that:

     (1)  The Report fully complies with the requirements of section 13(a) or
       15(d) of the Securities Exchange Act of 1934; and

     (2)   The information contained in the Report fairly presents, in  all
       material respects, the financial condition and
results of operation of the
       Company.


Date:  August 12, 2004




/s/ L. Paul Latham
L. Paul Latham
President and Chief Executive Officer
  of Southwest Royalties, Inc., the
  Managing General Partner of
  Southwest Royalties Institutional Income Fund X-C, L.P.

<PAGE>
                     CERTIFICATION PURSUANT TO             Exhibit
                                   32.2
                          19 U.S.C. SECTION 1350,
                          AS ADOPTED PURSUANT TO
               SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002


    In   connection  with  the  Quarterly  Report  of  Southwest  Royalties
Institutional Income Fund X-C, Limited Partnership (the "Company") on  Form
10-Q  for the period ending June 30, 2004 as filed with the Securities  and
Exchange  Commission on the date hereof (the "Report"), I,  Mel  G.  Riggs,
Chief  Financial  Officer of the Managing General Partner of  the  Company,
certify,  pursuant to 18 U.S.C.  1350, as adopted pursuant to  906  of  the
Sarbanes-Oxley Act of 2002, that:

     (1)  The Report fully complies with the requirements of section 13(a) or
       15(d) of the Securities Exchange Act of 1934; and

     (2)   The information contained in the Report fairly presents, in  all
       material respects, the financial condition and
results of operation of the
       Company.


Date: August 12, 2004




/s/ Mel G. Riggs
Mel G. Riggs
Vice President and Chief Financial Officer of
  Southwest Royalties, Inc., the
  Managing General Partner of
  Southwest Royalties Institutional Income Fund X-C, L.P.


<PAGE>