23
                                 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, 2005

                                    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.)

                         6 Desta Drive, Suite 6500
                           Midland, Texas 79705
                 (Address of principal executive offices)

                               432-682-6324
                      (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 23.

<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.

     BOE.   Equivalent  barrels of oil, with natural gas converted  to  oil
equivalents based on a ratio of six Mcf of natural gas to one Bbl of oil.

     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 a leasehold or
working  interest agrees to assign his interest in certain specific acreage
to  an  assignee,  retaining some interest, such as an  overriding  royalty
interest,  subject  to  the drilling of one (1)  or  more  wells  or  other
specified 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 oil and  gas  reserves
that  can  be  expected to be recovered from existing wells  with  existing
equipment and operating methods.

     Proved properties. Properties with proved reserves.

     Proved  oil  and gas reserves. The estimated quantities of crude  oil,
natural  gas, and natural gas liquids with geological and engineering  data
that  demonstrate  with  reasonable certainty to be recoverable  in  future
years   from  known  reservoirs  under  existing  economic  and   operating
conditions, i.e., prices and costs as of the date the estimate is made.

     Proved  undeveloped  reserves. Proved oil and gas  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, 2004, which are found in the Registrant's Form
10-K  Report  for  2004 filed with the Securities and Exchange  Commission.
The December 31, 2004 balance sheet included herein has been taken from the
Registrant's  2004 Form 10-K Report.  Operating results for the  three  and
nine-month  periods ended September 30, 2005 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

                                 Septembe  December
                                  r 30,      31,
                                   2005      2004
                                   ----      ----
                                 (unaudit
                                   ed)
Assets
----------

Current assets:
 Cash and cash equivalents    $  100,222   32,864
  Receivable  from  Managing     36,904    107,812
General Partner
   New   Mexico  withholding     512       -
prepayment
                                 --------  --------
                                 ----      ----
   Total current assets          137,638   140,676
                                 --------  --------
                                 ----      ----
Oil  and  gas  properties  -
using the full-
 method of accounting            2,395,60  2,395,60
                                 1         1
       Less      accumulated
depreciation,
         depletion       and     2,243,32  2,238,61
amortization                     1         4
                                 --------  --------
                                 ----      ----
      Net   oil   and    gas     152,280   156,987
properties
                                 --------  --------
                                 ----      ----
                              $  289,918   297,663
                                 =======   =======
Liabilities  and   Partners'
Equity
----------------------------
-----------

Current     liability      -  $  458       262
distribution payable
                                 --------  --------
                                 ----      ----

Asset retirement obligation      828,423   798,702
                                 --------  --------
                                 ----      ----

Partners' deficit:
 General partners                (94,543)  (91,248)
 Limited partners                (444,420  (410,053
                                 )         )
                                 --------  --------
                                 ----      ----
   Total partners' deficit       (538,963  (501,301
                                 )         )
                                 --------  --------
                                 ----      ----
                              $  289,918   297,663
                                 =======   =======












                  The accompanying notes are an integral
                    part of these financial statements.
<PAGE>

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

                                 Three Months Ended   Nine Months Ended
                                    September 30,       September 30,
                                   2005      2004      2005      2004
                                   -----    ------     -----     -----
Revenues
------------
Income from net profits        $ 153,440   89,475    374,618   249,065
interests
Interest                         347       84        618       186
Other                            -         -         -         250
                                 --------  --------  --------  --------
                                 --        -         --        --
                                 153,787   89,559    375,236   249,501
                                 --------  --------  --------  --------
                                 --        -         --        --
Expenses
------------
Depreciation, depletion and      1,571     2,249     4,708     8,249
amortization
Accretion of asset retirement    9,907     14,817    29,720    44,451
obligation
General and administrative       12,207    13,314    38,470    40,479
                                 --------  --------  --------  --------
                                 --        -         --        --
                                 23,685    30,380    72,898    93,179
                                 --------  --------  --------  --------
                                 --        -         --        --
Net income from continuing       130,102   59,179    302,338   156,322
operations

Results from discontinued
operation -
 sale of oil and gas lease -     -         -         -         (4,458)
See Note 3
                                 --------  --------  --------  --------
                                 --        -         --        --
Net income                     $ 130,102   59,179    302,338   151,864
                                 ======    =====     ======    ======

Net income allocated to:
 Managing General Partner      $ 11,851    5,529     27,634    14,410
                                 ======    =====     ======    ======
 General Partner               $ 1,317     614       3,071     1,601
                                 ======    =====     ======    ======
 Limited Partners              $ 116,934   53,036    271,633   135,853
                                 ======    =====     ======    ======
  Per limited partner unit
before discontinued
   operations                  $   19.54
                                           8.86      45.40     23.38
  Discontinued operations per         -         -          -
limited partner unit                                           (.67)
                                 --------  --------  --------  --------
                                 --        -         --        --
  Per limited partner unit     $   19.54
                                           8.86      45.40     22.71
                                 ======    =====     ======    ======










                  The accompanying notes are an integral
                    part of these financial statements.
<PAGE>

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

                                       Nine Months Ended
                                         September 30,
                                        2005      2004
                                        -----     -----
Cash flows from operating
activities
 Cash received from income from net $  445,014  191,513
profits interests
 Cash paid to suppliers                (38,470  (40,479)
                                       )
 Cash used in discontinued             -        (4,458)
operations
 Interest received                     618      186
 Other                                 -        250
                                       -------  ---------
                                       ---      -
  Net cash provided by operating       407,162  147,012
activities
                                       -------  ---------
                                       ---      -
Cash flows from financing
activities
 Distributions to partners             (340,00  (135,000)
                                       0)
 Increase in distribution payable      196      165
                                       -------  ---------
                                       ---      -
  Net cash used in financing           (339,80  (134,835)
activities                             4)
                                       -------  ---------
                                       ---      -

  Net increase in cash and cash        67,358   12,177
equivalents

 Beginning of period                   32,864   26,631
                                       -------  ---------
                                       ---      -
 End of period                      $  100,222  38,808
                                       ======   ======
Reconciliation of net income to net
cash
 provided by operating activities

Net income                          $  302,338  151,864

Adjustments to reconcile net income
to net
 cash provided by operating
activities

 Depreciation, depletion and           4,708    8,249
amortization
 Accretion of asset retirement         29,720   44,451
obligation
 Decrease (increase) in receivables    70,396   (57,552)
                                       -------  ---------
                                       ---      -
Net cash provided by operating      $  407,162  147,012
activities
                                       ======   ======











                  The accompanying notes are an integral
                    part of these financial statements.
<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 Blue Heel Company, a  wholly  owned
     subsidiary of Southwest Royalties, Inc., acquired the general  partner
     interest  from H.H. Wommack, III.   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 September 30, 2005,  and  for
     the  three  and  nine months ended September 30, 2005,  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, 2004.

     In September 2004, the Securities and Exchange Commission issued Staff
     Accounting  Bulletin No. 106 ("SAB 106"). SAB 106  expresses  the  SEC
     staff's views regarding SFAS No. 143 and its impact on both the  full-
     cost  ceiling  test  and  the calculation of  depletion  expense.   In
     accordance  with  SAB  106, beginning in the first  quarter  of  2005,
     undiscounted abandonment costs for wells to be drilled in  the  future
     to develop proved reserves are included in the unamortized cost of oil
     and  gas  properties, net of related salvage value,  for  purposes  of
     computing  depreciation,  depletion  and  amortization  ("DD&A").  The
     implementation  of  SAB  106 did not have a  material  impact  on  our
     financial statements.

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

                      Notes to Financial Statements

3.   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      Nine months ended
                          September 30,          September 30,
                         2005       2004         2005      2004
Loss from net profit
   interest            $   -      -           -          (4,458)

<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.  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 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.

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 September 30, 2005, 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
September 30, 2005, 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  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 depletion, depreciation, and amortization
("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

General Comparison of the Quarters Ended September 30, 2005 and 2004

The  following  table  provides certain information  regarding  performance
factors for the quarters ended September 30, 2005 and 2004:

                                    Three Months
                                       Ended         Percenta
                                                        ge
                                   September 30,     Increase
                                   2005      2004    (Decreas
                                                        e)
                                  -----     -----    --------
                                                        --
Oil production in barrels        5,926     5,487     8%
Gas production in mcf            3,315     2,861     16%
Total BOE                        6,479     5,964     9%
Average price per barrel  of  $   58.73              46%
oil                                        40.12
Average price per mcf of gas  $    6.44              46%
                                           4.41
Income   from  net   profits  $  153,440   89,475    71%
interests
Partnership distributions     $  140,000   65,000    115%
Limited              partner  $  126,000   58,500    115%
distributions
Per  unit  distribution   to  $   21.06              115%
limited partners                           9.78
Number  of  limited  partner     5,983     5,983
units

Income from net profits

The  Partnership's income from net profits interests increased to  $153,440
from   $89,475  for  the  quarters  ended  September  30,  2005  and  2004,
respectively,  an  increase of 71%.  The principal  factors  affecting  the
comparison  of  the  quarters ended September 30,  2005  and  2004  are  as
follows:

The average price for a barrel of oil received by the Partnership increased
during  the  quarter ended September 30, 2005 as compared  to  the  quarter
ended  September  30, 2004 by 46%, or $18.61 per barrel,  resulting  in  an
increase  of  approximately $110,300 in income from net profits  interests.
Oil  sales  represented 94% of total oil and gas sales during  the  quarter
ended  September  30,  2005  as compared to 95% during  the  quarter  ended
September 30, 2004.

The  average price for an mcf of gas received by the Partnership  increased
during  the same period by 46%, or $2.03 per mcf, resulting in an  increase
of approximately $6,700 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 $117,000.
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>

Oil production increased approximately 439 barrels or 8% during the quarter
ended  September  30, 2005 as compared to the quarter ended  September  30,
2004, resulting in an increase of approximately $17,600 in income from  net
profits interests.

Gas  production  increased approximately 454 mcf or  16%  during  the  same
period, resulting in an increase of approximately $2,000 in income from net
profits interests.

The  total increase in income from net profits interests due to the  change
in  production  is approximately $19,600.  The increase in gas  volumes  is
from improved gas production on one property.

Lease   operating  costs  and  production  taxes  were   51%   higher,   or
approximately $72,600 more during the quarter ended September 30,  2005  as
compared  to the quarter ended September 30, 2004.  The increase  in  lease
operating  costs  was primarily from a workover on a gas well  and  various
repair  and  maintenance work performed on several properties.   Production
taxes increased from the higher revenues resulting from higher oil and  gas
prices.

Costs and Expenses

Total costs and expenses decreased to $23,685 from $30,380 for the quarters
ended  September 30, 2005 and 2004, respectively, a decrease of  22%.   The
decrease  is  the result of lower accretion expense, depletion expense  and
general and administrative expense.

General  and  administrative costs consists of independent  accounting  and
engineering fees, computer services, postage, and Managing General  Partner
personnel  costs.   General  and  administrative  costs  decreased  8%   or
approximately  $1,100  during  the quarter  ended  September  30,  2005  as
compared to the quarter ended September 30, 2004.

Depletion  expense decreased to $1,571 for the quarter ended September  30,
2005  from $2,249 for the same period in 2004.  This represents a  decrease
of 30%.  The contributing factor to the decrease in depletion expense is in
relation  to  the  BOE depletion rate for the quarter ended  September  30,
2005,  which was $.24 applied to 6,479 BOE as compared to $.38  applied  to
5,964 BOE for the same period in 2004.  The lower depletion rate in 2005 is
due  to the upward revision in reserve estimates resulting from higher  oil
and gas prices.

Accretion  expense decreased to $9,907 for the quarter ended September  30,
2005  from $14,817 for the same period in 2004.  This represents a decrease
of  33%.   The  decrease  in accretion is from discontinuing  accretion  on
several wells that reached their projected end of life in 2004.




<PAGE>

General  Comparison of the Nine-Month Periods Ended September 30, 2005  and
2004

The  following  table  provides certain information  regarding  performance
factors for the nine-month periods ended September 30, 2005 and 2004:

                                    Nine Months
                                       Ended         Percenta
                                                        ge
                                   September 30,     Increase
                                   2005      2004    (Decreas
                                                        e)
                                   ----      ----    --------
                                                        --
Oil production in barrels        16,667    17,017    (2%)
Gas production in mcf            8,159     14,411    (43%)
Total BOE                        18,027    19,419    (7%)
Average price per barrel  of  $    52.16             48%
oil                                        35.25
Average price per mcf of gas  $     5.90             30%
                                           4.54
Income   from  net   profits  $  374,618   249,065   50%
interests
Partnership distributions     $  340,000   135,000   152%
Limited              partner  $  306,000   121,500   152%
distributions
Per  unit  distribution   to  $    51.14             152%
limited partners                           20.31
Number  of  limited  partner     5,983     5,983
units

Income from net profits

The  Partnership's income from net profits interests increased to  $374,618
from  $249,065  for  the nine months ended September  30,  2005  and  2004,
respectively,  an  increase of 50%.  The principal  factors  affecting  the
comparison  of  the nine months ended September 30, 2005 and  2004  are  as
follows:

The average price for a barrel of oil received by the Partnership increased
during  the  nine months ended September 30, 2005 as compared to  the  nine
months ended September 30, 2004 by 48%, or $16.91 per barrel, resulting  in
an increase of approximately $281,800 in income from net profits interests.
Oil sales represented 95% of total oil and gas sales during the nine months
ended  September 30, 2005 as compared to 90% during the nine  months  ended
September 30, 2004.

The  average price for an mcf of gas received by the Partnership  increased
during  the same period by 30%, or $1.36 per mcf, resulting in an  increase
of approximately $11,100 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 $292,900.
The  market price for oil and gas has been extremely volatile over the past
decade,  and management expects a certain amount of volatility to  continue
in the foreseeable future.

<PAGE>

Oil  production decreased approximately 350 barrels or 2% during  the  nine
months  ended  September  30, 2005 as compared to  the  nine  months  ended
September  30,  2004, resulting in a decrease of approximately  $12,300  in
income from net profits interests.

Gas  production  decreased approximately 6,252 mcf or 43% during  the  same
period, resulting in a decrease of approximately $28,400 in income from net
profits interests.

The  total decrease in income from net profits interests due to the  change
in production is approximately $40,700.  The decrease in gas volumes is due
to a gas well that ceased to produce in 2004.

Lease   operating  costs  and  production  taxes  were   30%   higher,   or
approximately $126,600 more during the nine months ended September 30, 2005
as  compared to the nine months ended September 30, 2004.  The increase  in
lease  operating  costs was primarily from a workover on  a  gas  well  and
various  repair  and  maintenance  work performed  on  several  properties.
Production  taxes  increased from the higher oil  revenues  resulting  from
higher oil prices.

Costs and Expenses

Total  costs  and expenses decreased to $72,898 from $93,179 for  the  nine
months ended September 30, 2005 and 2004, respectively, a decrease of  22%.
The  decrease  is the result of lower depletion expense, accretion  expense
and general and administrative expense.

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  5%   or
approximately  $2,000 during the nine months ended September  30,  2005  as
compared to the nine months ended September 30, 2004.

Depletion  expense decreased to $4,708 for the nine months ended  September
30,  2005  from  $8,249  for the same period in 2004.   This  represents  a
decrease  of  43%.   The contributing factor to the decrease  in  depletion
expense is in relation to the BOE depletion rate for the nine months  ended
September  30,  2005, which was $.26 applied to 18,027 BOE as  compared  to
$.42  applied  to  19,419  BOE for the same  period  in  2004.   The  lower
depletion  rate in 2005 is due to the upward revision in reserve  estimates
resulting from higher oil and gas prices.

Accretion  expense decreased to $29,720 for the nine months ended September
30,  2005  from  $44,451 for the same period in 2004.   This  represents  a
decrease of 33%.  The decrease in accretion is from discontinuing accretion
on several wells that reached their projected end of life in 2004.


<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 $407,200  in
the  nine  months  ended  September 30, 2005 as compared  to  approximately
$147,000 in the nine months ended September 30, 2004.

Cash flows used in financing activities were approximately $339,800 in  the
nine  months ended September 30, 2005 as compared to approximately $134,800
in  the  nine  months ended September 30, 2004.  The only use in  financing
activities was the distributions to partners.

Total  distributions during the nine months ended September 30,  2005  were
$340,000  of  which  $306,000 was distributed to the limited  partners  and
$34,000  to  the  general partners.  The per unit distribution  to  limited
partners during the nine months ended September 30, 2005 was $51.14.  Total
distributions during the nine months ended September 30, 2004 were $135,000
of  which  $121,500 was distributed to the limited partners and $13,500  to
the general partners.  The per unit distribution to limited partners during
the nine months ended September 30, 2004 was $20.31.

The  sources  for  the  2005  distributions of $340,000  was  oil  and  gas
operations  of  approximately  $407,200,  resulting  in  excess  cash   for
contingencies  or  subsequent  distributions.  The  sources  for  the  2004
distributions  of  $135,000  was oil and gas  operations  of  approximately
$147,000,   resulting  in  excess  cash  for  contingencies  or  subsequent
distributions.

Cumulative cash distributions of $4,024,061 have been made to the partners.
As  of  September 30, 2005, $3,639,142 or $608.25 per limited partner  unit
has  been  distributed  to the limited partners,  representing  a  122%  of
contributed capital.

As  of  September 30, 2005, the Partnership had approximately  $137,200  in
working  capital.   The  Managing  General  Partner  knows  of  no  unusual
contractual  commitments.  The partnership held many long-lived  properties
at  inception,  however  due to the restrictions  on  property  development
imposed  by  the partnership agreement, the Partnership cannot develop  its
non-producing  properties.   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.



<PAGE>


Recent Accounting Pronouncements

In  September  2004,  the Securities and Exchange Commission  issued  Staff
Accounting Bulletin No. 106 ("SAB 106"). SAB 106 expresses the SEC  staff's
views  regarding SFAS No. 143 and its impact on both the full-cost  ceiling
test and the calculation of depletion expense.  In accordance with SAB 106,
beginning in the first quarter of 2005, undiscounted abandonment costs  for
wells  to  be drilled in the future to develop proved reserves are included
in  the  unamortized cost of oil and gas properties, net of related salvage
value,  for  purposes of computing depreciation, depletion and amortization
("DD&A").  The implementation of SAB 106 did not have a material impact  on
our financial statements.


<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

The  Managing  General  Partner  has established  disclosure  controls  and
procedures   that  are  adequate  to  provide  reasonable  assurance   that
management will be able to collect, process and disclose both financial and
non-financial information, on a timely basis, in the Partnership's  reports
to  the  SEC.   Disclosure controls and procedures  include  all  processes
necessary  to  ensure  that material information  is  recorded,  processed,
summarized  and  reported within the time periods specified  in  the  SEC's
rules  and  forms,  and  is  accumulated and  communicated  to  management,
including our chief executive and chief financial officers, to allow timely
decisions regarding required disclosures.

     With respect to these disclosure controls and procedures:

          management  has  evaluated the effectiveness  of  the  disclosure
          controls  and procedures as of the end of the period  covered  by
          this report;

          this evaluation was conducted under the supervision and with  the
          participation  of management, including the chief  executive  and
          chief financial officers of the Managing General Partner; and

          it  is  the  conclusion of chief executive  and  chief  financial
          officers  of  the Managing General Partner that these  disclosure
          controls   and   procedures  are  effective  in   ensuring   that
          information  that is required to be disclosed by the  Partnership
          in   reports  filed  or  submitted  with  the  SEC  is  recorded,
          processed,  summarized  and  reported  within  the  time  periods
          specified in the rules and forms established by the SEC.

Internal Control Over Financial Reporting
There  has  not been any change in the Partnership's internal control  over
financial  reporting that occurred during the quarter ended  September  30,
2005  that  has materially affected, or is reasonably likely to  materially
affect, its 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
and Chief Financial Officer
                 Pursuant to 18 U.S.C. Section 1350, as adopted
                  Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002

<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/ L. Paul Latham
                                 L. Paul Latham
                                 President and Chief Executive Officer

Date:  November 14, 2005




<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: November 14, 2005            /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:  November 14, 2005           /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>
                                                               Exhibit 32.1

               CERTIFICATION OF CHIEF EXECUTIVE OFFICER AND
                          CHIEF FINANCIAL OFFICER

Pursuant to 18 U.S.C.  1350 and in connection with the accompanying  report
on  Form  10-Q for the period ended September 30, 2005 that is being  filed
concurrently with the Securities and Exchange Commission on the date hereof
(the  "Report"),  each of the undersigned officers of  Southwest  Royalties
Institutional Income Fund X-C, L.P. (the "Company"), hereby certifies 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.


                                   /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.

                                   November 14, 2005


                                   /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.

                                   November 14, 2005

<PAGE>