-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 Biwu2uWDbL1l46YghsoaTrLj13flUAS3c14lJDww1f+ODPKBoYeofW8QVOcBSLd7
 gFLMsC5p0ukucW34UOj0lQ==

<SEC-DOCUMENT>0000704051-05-000058.txt : 20050504
<SEC-HEADER>0000704051-05-000058.hdr.sgml : 20050504
<ACCEPTANCE-DATETIME>20050504164851
ACCESSION NUMBER:		0000704051-05-000058
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050504
FILED AS OF DATE:		20050504
DATE AS OF CHANGE:		20050504

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			LEGG MASON INC
		CENTRAL INDEX KEY:			0000704051
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
		IRS NUMBER:				521200960
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		100 LIGHT ST
		CITY:			BALTIMORE
		STATE:			MD
		ZIP:			21202-1476
		BUSINESS PHONE:		4105390000

	MAIL ADDRESS:	
		STREET 1:		100 LIGHT ST
		CITY:			BALTIMORE
		STATE:			MD
		ZIP:			21202-1476

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MULROY THOMAS P
		CENTRAL INDEX KEY:			0001206666

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08529
		FILM NUMBER:		05799842

	BUSINESS ADDRESS:	
		STREET 1:		100 LIGHT STREET
		CITY:			BALTIMORE
		STATE:			MD
		ZIP:			21202
		BUSINESS PHONE:		410-539-0000

	MAIL ADDRESS:	
		STREET 1:		LEGG MASON INC
		STREET 2:		100 LIGHT ST
		CITY:			BALTIMORE
		STATE:			MD
		ZIP:			21202
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-05-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000704051</issuerCik>
        <issuerName>LEGG MASON INC</issuerName>
        <issuerTradingSymbol>LM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001206666</rptOwnerCik>
            <rptOwnerName>MULROY THOMAS P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>LEGG MASON INC</rptOwnerStreet1>
            <rptOwnerStreet2>100 LIGHT ST</rptOwnerStreet2>
            <rptOwnerCity>BALTIMORE</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>21202</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-05-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10482</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.49</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100514</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>20.49</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-05-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10482</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>1998-07-23</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2006-07-22</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10482</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Employee stock option cummulatively exercisable annually in 20% increments commencing on the exercisable date indicated.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/Thomas C. Merchant, Attorney-in-fact for Thomas P. Mulroy</signatureName>
        <signatureDate>2005-05-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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