<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>3</documentType><periodOfReport>2003-05-22</periodOfReport>
    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000931336</issuerCik>
        <issuerName>DEAN FOODS CO/</issuerName>
        <issuerTradingSymbol>DF</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001237284</rptOwnerCik>
            <rptOwnerName>KLEIN RONALD H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Senior Vice President --</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionAmounts><transactionShares><value>14587.174</value></transactionShares></transactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><derivativeSecurity><securityTitle><value>Non-Qualified Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>29.25</value></conversionOrExercisePrice><exerciseDate><value>1999-01-02</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>1998-01-02</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5000</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Incentive Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>21.5625</value></conversionOrExercisePrice><exerciseDate><value>2004-01-22</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>2011-01-22</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>4636</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Incentive Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>21.5625</value></conversionOrExercisePrice><exerciseDate><value>2002-01-22</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>2011-01-22</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>13634</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Incentive Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>30.525</value></conversionOrExercisePrice><exerciseDate><value>2003-01-14</value><footnoteId id="F3"/></exerciseDate><expirationDate><value>2012-01-14</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>3276</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Non-Qualified Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>30.525</value></conversionOrExercisePrice><exerciseDate><value>2003-01-14</value><footnoteId id="F4"/></exerciseDate><expirationDate><value>2012-01-14</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>26724</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Non-Qualified Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>30.525</value></conversionOrExercisePrice><exerciseDate><value>2003-01-14</value><footnoteId id="F4"/></exerciseDate><expirationDate><value>2012-01-14</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>20000</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Incentive Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>37.19</value></conversionOrExercisePrice><exerciseDate><value>2004-01-06</value><footnoteId id="F4"/></exerciseDate><expirationDate><value>2013-01-06</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>2688</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Non-Qualified Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>37.19</value></conversionOrExercisePrice><exerciseDate><value>2004-01-06</value><footnoteId id="F4"/></exerciseDate><expirationDate><value>2013-01-06</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>22312</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Deferred Stock Units</value></securityTitle><conversionOrExercisePrice><value>0</value></conversionOrExercisePrice><exerciseDate><value>2004-01-07</value><footnoteId id="F5"/></exerciseDate><expirationDate><value>2013-01-07</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>9000</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">The shares of common stock subject to the Option are fully vested and exercisable.</footnote><footnote id="F2">The shares of common stock subject to the Option shall vest on January 22, 2004.</footnote><footnote id="F3">The shares of common stock subject to the Option shall on January 14, 2005.</footnote><footnote id="F4">The shares of common stock subject to the Option shall vest ratably in three equal increments commencing on the first anniversary of the grant date.</footnote><footnote id="F5">The reporting person has received an award of Deferred Stock Units (&amp;quot;DSUs&amp;quot;) which is a right to receive shares of common stock of the Issuer in the future, subject to the terms and conditions of the DSU Award Agreement.  The DSUs vest annually, on a prorata basis, over a five-year period.</footnote></footnotes><ownerSignature><signatureName>Ronald H. Klein</signatureName><signatureDate>2003-06-02</signatureDate></ownerSignature></ownershipDocument>

