FORM
      10-Q





SECURITIES
      AND EXCHANGE COMMISSION


WASHINGTON,
      D.C. 20549





(Mark
      One)





x  QUARTERLY
      REPORT PURSUANT TO SECTION 13 OR 15(d)


OF
      THE
      SECURITIES EXCHANGE ACT OF 1934





For
      the
      quarterly period ended March 31, 2007





OR





 ̈  TRANSITION
      REPORT PURSUANT TO SECTION 13 OR 15(d)


OF
      THE
      SECURITIES EXCHANGE ACT OF 1934





For
      the
      transition period from ________________ to ________________





Commission
      File Number 0-20298





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


(Exact
      name of registrant as specified in


its
      limited partnership agreement)





Delaware
            
            75-2374449(State
                or other jurisdiction
            
            (I.R.S.
                Employerof
                incorporation or organization)
            
            Identification
                No.)6
                Desta Drive, Suite 6500, Midland, Texas
            
            79705(Address
                of principal executive office)
            
            (Zip
                Code)





(432)
      682-6324


(Registrant's
      telephone number, including area code)





Not
      applicable


(Former
      name, former address and former fiscal year, if changed since last
      report)





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:YesxNo ̈





Indicate
                by check mark whether the registrant is a large accelerated filer,
                an
                accelerated filer, or a non-accelerated filer. See definition of
                “accelerated filer and large accelerated filer” in Rule 12b-2 of the
                Exchange Act.Large
                accelerated filer ̈
            
            Accelerated
                filer ̈
            
            Non-accelerated
                filerx





Indicate
                by check mark whether the registrant is a shell company (as defined
                in
                Rule 12b-2 of the Exchange Act). ̈Yes
            xNo





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.











**Table
                of Contents****Page**Glossary
            3**Part
                I - FINANCIAL INFORMATION**Item
                1.
            Financial
                Statements
            5Balance
                Sheets as of March 31, 2007 and December 31,
                2006
            6Statements
                of Operations for the three months ended March 31,
                2007 and 2006
            7Statements
                of Cash flows for the three months ended March 31,
                2007 and 2006
            8Item
                2.
            Management’s
                Discussion and Analysis of Financial Condition
                and Results of Operations
            11Item
                3.
            Quantitative
                and Qualitative Disclosures About Market
                Risk
            15Item
                4.
            Controls
                and Procedures
            15**Part
                II - OTHER INFORMATION**Item
                1.
            Legal
                Proceedings
            16Item
                1A.
            Risk
                Factors
            16Item
                2.
            Unregistered
                Sales of Equity Securities and Use of
                Proceeds
            16Item
                3.
            Defaults
                Upon Senior Securities
            16Item
                4.
            Submission
                of Matter to a Vote of Security
                Holders
            16Item
                5.
            Other
                Information
            16Item
                6.
            Exhibits
            16Signatures
            17


2


**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
      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.








3


*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.





*Standardized
      measure of discounted future net cash flows.* Present
      value ** of
      proved
      reserves, as adjusted to give effect to estimated future abandonment costs,
      net
      of the estimated salvage value of related equipment.





*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.








4


**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, 2006, which are found
      in
      the Registrant's Form 10-K Report for 2006 filed with the Securities and
      Exchange Commission. The December 31, 2006 balance sheet included herein has
      been taken from the Registrant's 2006 Form 10-K Report. Operating results for
      the three month period ended March 31, 2007 are not necessarily indicative
      of the results that may be expected for the full year.











5


**Southwest
      Royalties Institutional Income Fund X-C,
      L.P.**


**Balance
      Sheets**








**March
                31,**
            
            **December
                31,****2007**
            
            **2006****(unaudited)****Assets**Current
                assets:Cash
                and cash equivalents
            
            $
            32,819
            
            $
            29,985Receivable
                from Managing General Partner
            
            
            32,777
            
            
            28,153New
                Mexico income tax deposits
            
            
            3,645
            
            
            3,047Total
                current assets
            
            
            69,241
            
            
            61,185Oil
                and gas properties - using the full-costmethod
                of accounting
            
            
            2,668,028
            
            
            2,668,028Less
                accumulated depreciation,depletion
                and amortization
            
            
            2,263,950
            
            
            2,255,562Net
                oil and gas properties
            
            
            404,078
            
            
            412,466$
            473,319
            
            $
            473,651**Liabilities
                and Partners' Equity (Deficit)**Asset
                retirement obligation
            
            $
            1,001,428
            
            
            991,790Partners'
                (deficit):General
                partners
            
            
            (91,629
            )
            
            (91,471
            )Limited
                partners
            
            
            (436,480
            )
            
            (426,668
            )Total
                partners' (deficit)
            
            
            (528,109
            )
            
            (518,139
            )$
            473,319
            
            $
            473,651




















































The
      accompanying notes are an integral


part
      of
      these financial statements.


6


**Southwest
      Royalties Institutional Income Fund X-C,
      L.P.**


**Statements
      of Operations**


**(unaudited)**








**Three
                Months Ended****March
                31,****2007**
            
            **2006****Revenues**Income
                from net profits interests
            
            $
            52,947
            
            $
            95,191Interest
            
            
            183
            
            
            480Gain
                on sale of property and equipment
            
            
            -
            
            
            144,90053,130
            
            
            240,571**Expenses**Depreciation,
                depletion and amortization
            
            
            8,388
            
            
            -Accretion
                of asset retirement obligations
            
            
            22,296
            
            
            11,882General
                and administrative
            
            
            7,416
            
            
            13,61638,100
            
            
            25,498Net
                income
            
            $
            15,030
            
            $
            215,073Net
                income allocated to:Managing
                General Partner
            
            $
            2,108
            
            $
            19,356General
                partner
            
            $
            234
            
            $
            2,151Limited
                partners
            
            $
            12,688
            
            $
            193,566Per
                limited partner unit
            
            $
            2.12
            
            $
            32.35


















































The
      accompanying notes are an integral


part
      of
      these financial statements.


7


**Southwest
      Royalties Institutional Income Fund X-C,
      L.P.**


**Statements
      of Cash Flows**


**(unaudited)**








**Three
                Months Ended****March
                31,****2007**
            
            **2006**Cash
                flows from operating activities:Cash
                received from net profits interest
            
            $
            35,067
            
            $
            153,855Cash
                paid to suppliers
            
            
            (7,416
            )
            
            (13,616
            )Interest
                received
            
            
            183
            
            
            480Net
                cash provided by operating activities
            
            
            27,834
            
            
            140,719Cash
                flows used in financing activities:Distributions
                to partners
            
            
            (25,000
            )
            
            (140,000
            )Net
                increase in cash and cash equivalents
            
            
            2,834
            
            
            719Beginning
                of period
            
            
            29,985
            
            
            51,969End
                of period
            
            $
            32,819
            
            $
            52,688Reconciliation
                of net income to net cashprovided
                by operating activities:Net
                income
            
            $
            15,030
            
            $
            215,073Adjustments
                to reconcile net income tonet
                cash provided by operating activities:Depreciation,
                depletion and amortization
            
            
            8,388
            
            
            -Settlement
                of asset retirement obligationsfor
                plugged and abandoned wells
            
            
            (12,658
            )
            
            -Gain
                on sale of property and equipment
            
            
            -
            
            
            (144,900
            )Accretion
                of asset retirement obligations
            
            
            22,296
            
            
            11,882(Increase)
                decrease in receivables and deposits
            
            
            (5,222
            )
            
            58,664Net
                cash provided by operating activities
            
            $
            27,834
            
            $
            140,719



































The
      accompanying notes are an integral


part
      of
      these financial statements.


8


**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. Revenues, costs and expenses are allocated as
      follows:





Limited
            
            GeneralPartners
            
            PartnersInterest
                income on capital contributions
            100%
            
            -Oil
                and gas sales
            90%
            
            10%All
                other revenues
            90%
            
            10%Organization
                and offering costs (1)
            100%
            
            -Syndication
                costs
            100%
            
            -Amortization
                of organization costs
            100%
            
            -Property
                acquisition costs
            100%
            
            -Gain/loss
                on property disposition
            90%
            
            10%Operating
                and administrative costs (2)
            90%
            
            10%Depreciation,
                depletion and amortization of oil and gas properties
            100%
            
            -All
                other costs
            90%
            
            10%




(1)
            All
                organization costs in excess of 3% of initial capital contributions
                will
                be paid by the Managing General Partner and will be treated as a
                capital
                contribution. The Partnership paid the Managing General Partner an
                amount
                equal to 3% of initial capital contributions for such organization
                costs.





(2)
            Administrative
                costs in any year, which exceed 2% of capital contributions shall
                be paid
                by the Managing General Partner and will be treated as a capital
                contribution.





**2.** **Summary
      of Significant Accounting Policies**


The
      interim financial information as of March 31, 2007, and for the three months
      ended March 31, 2007, 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,
      2006.





In
      June
      2006, the Financial Accounting Standards Board (“FASB”) issued FASB
      Interpretation No. 48 “Accounting for Uncertainty in Income Taxes” (“FIN48”) to
      clarify the manner in which enterprises account for uncertainties in their
      provisions for income taxes. Generally, the standard presented by FIN 48 is
      a
“more likely than not” standard and is intended to enhance the relevancy and
      comparability of financial reporting by companies. FIN 48 is effective for
      fiscal years beginning after December 31, 2006. FIN 48 has not had an impact
      on
      the Partnership’s financial statements since its adoption January 1,
      2007.





9


**Southwest
      Royalties Institutional Income Fund X-C, L.P.**


**(a
      Delaware limited partnership)**





**Notes
      to Financial Statements**





**3.** **Abandonment
      Obligations**


The
      Partnership follows the provisions of Statement of Financial Accounting
      Standards No. 143 “Accounting for Asset Retirement Obligations” (“SFAS 143”), as
      amended.  SFAS 143 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 capitalize an equal amount as a cost of the
      asset.  The cost associated with the abandonment obligations, along with
      any estimated salvage value, is included in the computation of depreciation,
      depletion and amortization.





Changes
      in abandonment obligations for the three months ended March 31, 2007 and 2006
      are as follows:





2007
            
            2006Beginning
                of period
            
            $
            991,790
            
            
            705,381Reduction
                of obligations due to wells plugged and abandoned
            
            
            (12,658
            )Accretion
                expense
            
            
            22,296
            
            
            11,882Gain
                on sale of property and equipment
            
            
            -
            
            
            (144,900
            )End
                of period
            
            $
            1,001,428
            
            
            572,363





10


**Item2.** **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 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
      decline 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 March 31, 2007, the net capitalized costs did not exceed the
      estimated present value of oil and gas reserves.





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 March 31, 2007, there were no timing differences,
      which resulted in a deficit net profit interest.


11


*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.





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.








12


**Supplemental
      Information**


The
      following unaudited information is intended to supplement the financial
      statements included in this Form 10-Q with data that is not readily available
      from those statements.





**Three
                Months Ended****March
                31,****2007**
            
            **2006**Oil
                production in barrels
            
            
            4,038
            
            
            4,401Gas
                production in mcf
            
            
            2,647
            
            
            2,168Total
                (BOE)
            
            
            4,479
            
            
            4,762Average
                price per barrel of oil
            
            $
            51.98
            
            $
            57.32Average
                price per mcf of gas
            
            $
            6.65
            
            $
            5.98Partnership
                distributions
            
            $
            25,000
            
            $
            140,000Limited
                partner distributions
            
            $
            22,500
            
            $
            126,000Per
                unit distribution to limited partners
            
            $
            3.76
            
            $
            21.06Number
                of limited partner units
            
            
            5,983
            
            
            5,983





**Operating
      Results**


The
      following discussion compares our results for the quarters ended March 31,
      2007
      and 2006. Unless otherwise indicated, references to 2007 and 2006 within this
      section refer to the respective quarterly period.





**Income
      from net profits**


Comparing
      2007 to 2006, oil and gas sales decreased $37,700, of which price variances
      accounted for a $19,800 decrease and production variances accounted for a
      $17,900 decrease.





Production
      in 2007 (on a BOE basis) was 6% lower than 2006. Our oil production decreased
      8%
      in 2007 due primarily to normal production decline. Our gas production was
      22%
      higher in 2007 than 2006 due primarily to one well that was shut-in for six
      weeks in 2006.





In
      2007,
      our realized oil price was 9% lower than 2006, while our realized gas price
      was
      11% higher. Historically, the markets for oil and gas have been volatile, and
      they are likely to continue to be volatile. We have very little control over
      the
      prices we receive for our production at the wellhead since most of our physical
      marketing arrangements are market-sensitive.





Oil
      and
      gas production costs on a BOE basis increased from $35.70 per BOE in 2006 to
      $38.97 per BOE in 2007. The increase in oil and gas production costs in 2007
      was
      due primarily to surface and subsurface repairs on one property.





**Expenses**


Depletion
      on a BOE basis increased 100% in 2007. Comparing 2007 to 2006, depletion expense
      increased $8,388, primarily due to rate variances related to revisions of fourth
      quarter 2007 asset retirement obligations.





Accretion
      expense increased 88% in 2007 due primarily to revisions in previous estimates
      related to increased costs to plug wells.





General
      and administrative (“G&A”) expenses were 46% lower in 2007 due primarily to
      lower audit fees paid than previously accrued.





**Texas
      Margin Taxes**


In
      May
      2006, the State of Texas adopted House Bill 3, which modified the state’s
      franchise tax structure, replacing the previous tax based on capital or earned
      surplus with a margin tax (the “Texas Margin Tax”) effective with franchise tax
      reports filed on or after January 1, 2008. The Texas margin Tax is computed
      by
      applying the applicable tax rate (1% for the Partnership’s business) to the
      profit margin, which is generally determined by total revenue less either cost
      of goods sold or compensation as applicable. However the Partnership believes,
      based on its interpretation, that the Texas Margin Tax does not apply to the
      Partnership since substantially all of its income is derived from a net profits
      interest.








13


**Liquidity
      and Capital Resources**


Partnership
      distributions during the quarter ending March 31, 2007 were $25,000, of which
      $22,500 was distributed to the limited partners and $2,500 to the general
      partners. Cumulative cash distributions of $4,600,175 have been made to the
      general and limited partners as of March 31, 2007. As of March 31, 2007,
      $4,157,410 or $694.87 per limited partner unit has been distributed to the
      limited partners, representing 139% of contributed capital.





**Recent
      Accounting Pronouncements**


In
      June
      2006, the Financial Accounting Standards Board (“FASB”) issued FASB
      Interpretation No. 48 “Accounting for Uncertainty in Income Taxes” (“FIN48”) to
      clarify the manner in which enterprises account for uncertainties in their
      provisions for income taxes. Generally, the standard presented by FIN 48 is
      a
“more likely than not” standard and is intended to enhance the relevancy and
      comparability of financial reporting by companies. FIN 48 is effective for
      fiscal years beginning after December 31, 2006. FIN
      48
      has not had an impact on the Partnership’s financial statements since its
      adoption January 1, 2007.








14


**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 March 31, 2007 that has
      materially affected, or is reasonably likely to materially affect, its internal
      control over financial reporting.





15


**PART
      II. - OTHER INFORMATION**





**Item1.**  **Legal
      Proceedings**





None





**Item
      1A.**  **Risk
      Factors**





In
      evaluating all forward-looking statements, you should specifically consider
      various factors that may cause actual results to vary from those contained
      in
      the forward-looking statements. Our risk factors are included in our Annual
      Report on Form 10-K for the year ended December 31, 2006, as filed
      with the U.S. Securities and Exchange Commission on April 16, 2007 and available
      at www.sec.gov. There have been no material changes to these risk factors since
      the filing of our Form 10-K.





**Item
      2.**  **Unregistered
      Sales of Equity Securities and Use of Proceeds**





None





**Item
      3.**  **Defaults
      Upon Senior Securities**





None





**Item4.**  **Submission
      of Matter to a Vote of Security Holders**





None





**Item
      5.**  **Other
      Information**





None








**Item
      6.**  **Exhibits**





(a)  Exhibits:





31.1
            Rule
                13a-14(a)/15d-14(a) Certification31.2
            Rule
                13a-14(a)/15d-14(a) Certification32.1
            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














16


**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 FundX-C,
                L.P., a Delaware limited partnershipBy:
            Southwest
                Royalties, Inc., ManagingGeneral
                PartnerBy:
            /s/
                L. Paul LathamL.
                Paul LathamPresident
                and Chief Executive OfficerDate:
            May
                14, 2007





17