<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-12-16</periodOfReport>
    <issuer>
        <issuerCik>0000010456</issuerCik>
        <issuerName>BAXTER INTERNATIONAL INC</issuerName>
        <issuerTradingSymbol>BAX</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001161662</rptOwnerCik>
            <rptOwnerName>RIEDEL NORBERT G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ONE BAXTER PARKWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DEERFIELD</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60015</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Senior Vice President</officerTitle></reportingOwnerRelationship></reportingOwner><derivativeTable><derivativeTransaction><securityTitle><value>Deferred Compensation Plan-Baxter Stock Fund </value></securityTitle><conversionOrExercisePrice><footnoteId id="F1"/></conversionOrExercisePrice><transactionDate><value>2003-12-16</value><footnoteId id="F2"/></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>I</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>6960.7</value><footnoteId id="F3"/></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><footnoteId id="F4"/></exerciseDate><expirationDate><footnoteId id="F4"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock $1 par value</value></underlyingSecurityTitle><underlyingSecurityShares><value>6960.7</value><footnoteId id="F3"/></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>0</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">one for one</footnote><footnote id="F2">Reporting person elected to allocate compensation deferred under Baxter's Deferred Compensation Plan (&quot;Plan&quot;), including compensation previously deferred into the Baxter Common Stock Fund notional investment alternative, to a benchmark investment alternative other than the Baxter Common Stock Fund, effective as of January 1, 2004.  The value of the reporting person's Plan account is based on the performance of the benchmark investment fund(s) selected by the reporting person.</footnote><footnote id="F3">Equal to the reporting person's Baxter Common Stock Fund account balance as of December 16, 2003, divided by $ 30.50 which was the closing stock price of Baxter common stock on December 16, 2003, as reported by the New York Stock Exchange.</footnote><footnote id="F4">Reporting person's account balance under the Plan is payable in cash after termination of employment or on a future date designated in advance by the reporting person, subject to the terms of the Plan.  The reporting person may change investment elections quarterly.</footnote></footnotes><remarks/><ownerSignature><signatureName>William M. Link, Attorney-in-Fact for Norbert G. Riedel</signatureName><signatureDate>2003-12-17</signatureDate></ownerSignature></ownershipDocument>

