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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 ENFewYzbJF6msKY1R7h81nybMr+pn5XjLLBIsriDelLZ6xnPECpVt0k5MooeUviT
 B4/hTRZ6bKMNT4zR7KTiow==

<SEC-DOCUMENT>0001179110-05-016923.txt : 20050823
<SEC-HEADER>0001179110-05-016923.hdr.sgml : 20050823
<ACCEPTANCE-DATETIME>20050823191318
ACCESSION NUMBER:		0001179110-05-016923
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050822
FILED AS OF DATE:		20050823
DATE AS OF CHANGE:		20050823

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SCHWARTZ ALFRED J
		CENTRAL INDEX KEY:			0001196543

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-31267
		FILM NUMBER:		051044654

	BUSINESS ADDRESS:	
		STREET 1:		2765 FM 3093
		CITY:			GARDEN CITY
		STATE:			TX
		ZIP:			79739
		BUSINESS PHONE:		9156835422

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CAP ROCK ENERGY CORP
		CENTRAL INDEX KEY:			0001129162
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC SERVICES [4911]
		IRS NUMBER:				752794300
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		500 WEST WALL STREET SUITE 400
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79701
		BUSINESS PHONE:		2142373223

	MAIL ADDRESS:	
		STREET 1:		500 WEST WALL STREET SUITE 400
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79701
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-08-22</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001129162</issuerCik>
        <issuerName>CAP ROCK ENERGY CORP</issuerName>
        <issuerTradingSymbol>RKE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001196543</rptOwnerCik>
            <rptOwnerName>SCHWARTZ ALFRED J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2765 FM 3093</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>GARDEN CITY</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>79739</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-08-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>I</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>64</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>323947</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The Trust holds shares for the benefit of the former members of Cap Rock Electric Cooperative whose current addresses are unknown.  This form is being filed by Mr. Alfred J. Schwartz, Trustee, for the benefit of distributing shares to beneficial owners who have been found.</footnote>
        <footnote id="F2">By Cap Rock Energy Corporation Shareholders' Trust</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Alfred J. Schwartz</signatureName>
        <signatureDate>2005-08-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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