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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0001209191-10-049761.txt : 20101007
<SEC-HEADER>0001209191-10-049761.hdr.sgml : 20101007
<ACCEPTANCE-DATETIME>20101007171534
ACCESSION NUMBER:		0001209191-10-049761
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100929
FILED AS OF DATE:		20101007
DATE AS OF CHANGE:		20101007

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			KEITHLEY INSTRUMENTS INC
		CENTRAL INDEX KEY:			0000054991
		STANDARD INDUSTRIAL CLASSIFICATION:	INSTRUMENTS FOR MEAS & TESTING OF ELECTRICITY & ELEC SIGNALS [3825]
		IRS NUMBER:				340794417
		STATE OF INCORPORATION:			OH
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		28775 AURORA RD
		CITY:			SOLON
		STATE:			OH
		ZIP:			44139
		BUSINESS PHONE:		2162480400

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DANAHER CORP /DE/
		CENTRAL INDEX KEY:			0000313616
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INSTRUMENTS FOR MEASUREMENT, DISPLAY, AND CONTROL [3823]
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-09965
		FILM NUMBER:		101114491

	BUSINESS ADDRESS:	
		STREET 1:		2099 PENNSYLVANIA AVE N.W., 12TH FLOOR
		CITY:			WASHINGTON
		STATE:			DC
		ZIP:			20006
		BUSINESS PHONE:		2028280850

	MAIL ADDRESS:	
		STREET 1:		2099 PENNSYLVANIA AVE. N.W., 12TH FLOOR
		CITY:			WASHINGTON
		STATE:			DC
		ZIP:			20006

	FORMER NAME:	
		FORMER CONFORMED NAME:	DMG INC
		DATE OF NAME CHANGE:	19850221

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Aegean Acquisition Corp.
		CENTRAL INDEX KEY:			0001502907
		STATE OF INCORPORATION:			OH
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-09965
		FILM NUMBER:		101114492

	BUSINESS ADDRESS:	
		STREET 1:		2099 PENNSYLVANIA AVENUE
		STREET 2:		12TH FLOOR
		CITY:			WASHINGTON
		STATE:			DC
		ZIP:			20006
		BUSINESS PHONE:		2028280850

	MAIL ADDRESS:	
		STREET 1:		2099 PENNSYLVANIA AVENUE
		STREET 2:		12TH FLOOR
		CITY:			WASHINGTON
		STATE:			DC
		ZIP:			20006
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>doc3.xml
<DESCRIPTION>FORM 3 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2010-09-29</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000054991</issuerCik>
        <issuerName>KEITHLEY INSTRUMENTS INC</issuerName>
        <issuerTradingSymbol>KEI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000313616</rptOwnerCik>
            <rptOwnerName>DANAHER CORP /DE/</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2099 PENNSYLVANIA AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>WASHINGTON</rptOwnerCity>
            <rptOwnerState>DC</rptOwnerState>
            <rptOwnerZipCode>20006</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001502907</rptOwnerCik>
            <rptOwnerName>Aegean Acquisition Corp.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2099 PENNSYLVANIA AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>WASHINGTON</rptOwnerCity>
            <rptOwnerState>DC</rptOwnerState>
            <rptOwnerZipCode>20006</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Class B Common Shares</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This Form 3 is being filed as a result of that certain Voting Agreement, dated as of September 29, 2010, by and among Danaher Corporation (&quot;Parent&quot;), Aegean Acquisition Corp. (&quot;Merger Sub&quot;) and Keithley Investment Co. Limited Partnership (&quot;Partnership&quot;), covering such number of the Partnership's Class B common shares representing 19.99% of the voting power of the Issuer. The Voting Agreement was entered into in connection with the proposed acquisition of the Issuer by Parent and Merger Sub.  For additional information regarding the Voting Agreement and the acquisition of the Issuer, see Schedule 13D filed by Parent and Merger Sub with the Securities and Exchange Commission on October 7, 2010.  Parent and Merger Sub expressly disclaim any beneficial ownership of the Issuer's common shares and Class B common shares.</footnote>
    </footnotes>

    <remarks>Exhibit 99 - Joint Filer Information
Name: Aegean Acquisition Corp.
Address: 2099 Pennsylvania Avenue, 12th Floor
Washington, DC 20006
Designated Filer: Danaher Corporation
Issuer &amp; Ticker Symbol: Keithley Instruments, Inc. (NYSE: KEI)
Date of Event Requiring Statement: September 29, 2010</remarks>

    <ownerSignature>
        <signatureName>/s/ James F. O'Reilly, Associate General Counsel and Secretary, Danaher Corporation

/s/ James F. O'Reilly, Vice President and Secretary, Aegean Acquisition Corp.</signatureName>
        <signatureDate>2010-10-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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