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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0000940394-08-000610.txt : 20080415
<SEC-HEADER>0000940394-08-000610.hdr.sgml : 20080415
<ACCEPTANCE-DATETIME>20080415103502
ACCESSION NUMBER:		0000940394-08-000610
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080314
FILED AS OF DATE:		20080415
DATE AS OF CHANGE:		20080415

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			EATON VANCE INSTITUTIONAL SENIOR FLOATING RATE FUND
		CENTRAL INDEX KEY:			0001080310
		IRS NUMBER:				043457431
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		THE EATON VANCE BUILDING
		STREET 2:		255 STATE STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02109
		BUSINESS PHONE:		617-598-8880

	MAIL ADDRESS:	
		STREET 1:		THE EATON VANCE BUILDING
		STREET 2:		255 STATE STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02109

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Saltonstall George W
		CENTRAL INDEX KEY:			0001349129

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	811-09249
		FILM NUMBER:		08756141

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		617-482-8260

	MAIL ADDRESS:	
		STREET 1:		255 STATE STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02109
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>sal55.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-03-14</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001080310</issuerCik>
        <issuerName>EATON VANCE INSTITUTIONAL SENIOR FLOATING RATE FUND</issuerName>
        <issuerTradingSymbol>EIFRX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001349129</rptOwnerCik>
            <rptOwnerName>Saltonstall George W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>THE EATON VANCE BUILDING</rptOwnerStreet1>
            <rptOwnerStreet2>255 STATE STREET</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02109</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Management Committee</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <ownerSignature>
        <signatureName>By: Paul M. O'Neil / Attorney in Fact</signatureName>
        <signatureDate>2008-04-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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