<SUBMISSION>
<ACCESSION-NUMBER>0001179110-05-005760
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20050315
<FILING-DATE>20050316
<DATE-OF-FILING-DATE-CHANGE>20050316
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>RUSH ENTERPRISES INC \TX\
<CIK>0001012019
<ASSIGNED-SIC>5500
<IRS-NUMBER>741733016
<STATE-OF-INCORPORATION>TX
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>555 IH 35 SOUTH
<CITY>NEW BRAUNFELS
<STATE>TX
<ZIP>78130
<PHONE>8306265200
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>555 IH 35 SOUTH
<CITY>NEW BRAUNFELS
<STATE>TX
<ZIP>78130
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Thor James E
<CIK>0001300922
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-20797
<FILM-NUMBER>05683821
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>830-626-5200
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>C/O RUSH ENTERPRISES, INC.
<STREET2>P. O. BOX 34630
<CITY>SAN ANTONIO
<STATE>TX
<ZIP>78265
</MAIL-ADDRESS>
</REPORTING-OWNER>
<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>2005-03-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001012019</issuerCik>
        <issuerName>RUSH ENTERPRISES INC \TX\</issuerName>
        <issuerTradingSymbol>RUSH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001300922</rptOwnerCik>
            <rptOwnerName>Thor James E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>555 IH 35 SOUTH, SUITE 500</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW BRAUNFELS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>78130</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP - Retail Sales</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>15.76</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>11000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.76</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-03-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>11000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>11000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Options may be exercised in increments of 1/3 on each anniversary of the grant date beginning on the third anniversary of the grant date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Steven L. Keller, by power of attorney</signatureName>
        <signatureDate>2005-03-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
