<SUBMISSION>
<ACCESSION-NUMBER>0001238550-07-000079
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20071217
<FILING-DATE>20071219
<DATE-OF-FILING-DATE-CHANGE>20071219
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>DREW INDUSTRIES INC
<CIK>0000763744
<ASSIGNED-SIC>3714
<IRS-NUMBER>133250533
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>200 MAMARONECK AVE
<CITY>WHITE PLAINS
<STATE>NY
<ZIP>10601
<PHONE>9144289098
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>200 MAMARONECK AVE
<CITY>WHITE PLAINS
<STATE>NY
<ZIP>10601
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>LOWE JOHN B JR
<CIK>0001281085
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-13646
<FILM-NUMBER>071316038
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>901 W WALNUT HILL LANE
<STREET2>MALL STATION 6B 3
<CITY>IRVING
<STATE>TX
<ZIP>73030
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-12-17</periodOfReport>

    <issuer>
        <issuerCik>0000763744</issuerCik>
        <issuerName>DREW INDUSTRIES INC</issuerName>
        <issuerTradingSymbol>DW</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001281085</rptOwnerCik>
            <rptOwnerName>LOWE JOHN B JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O DREW INDUSTRIES INCORPORATED</rptOwnerStreet1>
            <rptOwnerStreet2>200 MAMARAONECK AVENUE</rptOwnerStreet2>
            <rptOwnerCity>WHITE PLAINS</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10601</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>28.09</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-12-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2008-12-17</value>
            </exerciseDate>
            <expirationDate>
                <value>2013-12-17</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>22500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Fredric M. Zinn, on behalf of John B. Lowe, Jr.</signatureName>
        <signatureDate>2007-12-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
