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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 WS8zVf0eUZQxmplmqHbpvwt8JgSfH8AH2gVqRqdi6Gz68kbk0nKToO02vWgzlf+U
 786srM3qC2PGFKu/lOo/cA==

<SEC-DOCUMENT>0001226579-06-000044.txt : 20060215
<SEC-HEADER>0001226579-06-000044.hdr.sgml : 20060215
<ACCEPTANCE-DATETIME>20060215140113
ACCESSION NUMBER:		0001226579-06-000044
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051201
FILED AS OF DATE:		20060215
DATE AS OF CHANGE:		20060215

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			DONALDSON CO INC
		CENTRAL INDEX KEY:			0000029644
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL & COMMERCIAL FANS & BLOWERS & AIR PURIFYING EQUIP [3564]
		IRS NUMBER:				410222640
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0731

	BUSINESS ADDRESS:	
		STREET 1:		1400 W. 94TH ST.
		CITY:			MINNEAPOLIS
		STATE:			MN
		ZIP:			55431
		BUSINESS PHONE:		6128873131

	MAIL ADDRESS:	
		STREET 1:		1400 W 94TH STREET
		CITY:			MINNEAPOLIS
		STATE:			MN
		ZIP:			55431

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			EUGSTER JACK W
		CENTRAL INDEX KEY:			0000904033
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-07891
		FILM NUMBER:		06621238

	BUSINESS ADDRESS:	
		STREET 1:		10400 YELLOW CIRCLE DRIVE
		CITY:			MINNETONKA
		STATE:			MN
		ZIP:			55343
		BUSINESS PHONE:		6129318044

	MAIL ADDRESS:	
		STREET 1:		7075 FLYING CLOUD DR
		CITY:			EDEN PRAIRE
		STATE:			MN
		ZIP:			55344
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2005-12-01</periodOfReport>

    <dateOfOriginalSubmission>2005-12-05</dateOfOriginalSubmission>

    <issuer>
        <issuerCik>0000029644</issuerCik>
        <issuerName>DONALDSON CO INC</issuerName>
        <issuerTradingSymbol>DCI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000904033</rptOwnerCik>
            <rptOwnerName>EUGSTER JACK W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1400 WEST 94TH</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BLOOMINGTON</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55431</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-12-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1461</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>30.22</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>42014</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>33.20</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-12-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7200</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-12-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2015-12-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7200</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7200</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Correction to Amount of Securities Owned due to amended Form 5 filing for July 2002 reporting gift of 2,000 shares on December 6, 2001.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Norman C. Linnell, Attorney-in-fact for Jack Eugster</signatureName>
        <signatureDate>2006-02-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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