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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 R7LNNDVu850uzpWEdolHS/bWoCBeedJdZEwQSEyweqyteemJe7F+z/t6eb1u9M7u
 DGgye0VtYaAinZ2C0wEfVA==

<SEC-DOCUMENT>0001390614-09-000001.txt : 20090911
<SEC-HEADER>0001390614-09-000001.hdr.sgml : 20090911
<ACCEPTANCE-DATETIME>20090911164614
ACCESSION NUMBER:		0001390614-09-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20090910
FILED AS OF DATE:		20090911
DATE AS OF CHANGE:		20090911

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Brown Denis R
		CENTRAL INDEX KEY:			0001314175

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-06549
		FILM NUMBER:		091065777

	MAIL ADDRESS:	
		STREET 1:		C/O AMERICAN SCIENCE & ENGINEERING,INC
		STREET 2:		829 MIDDLESEX TURNPIKE
		CITY:			BILLERICA
		STATE:			MA
		ZIP:			01821

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			AMERICAN SCIENCE & ENGINEERING INC
		CENTRAL INDEX KEY:			0000005768
		STANDARD INDUSTRIAL CLASSIFICATION:	X-RAY APPARATUS & TUBES & RELATED IRRADIATION APPARATUS [3844]
		IRS NUMBER:				042240991
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			0331

	BUSINESS ADDRESS:	
		STREET 1:		C/O AS&E
		STREET 2:		829 MIDDLESEX TURNPIKE
		CITY:			BILLERICA
		STATE:			MA
		ZIP:			01821
		BUSINESS PHONE:		9782628700

	MAIL ADDRESS:	
		STREET 1:		C/O AS&E
		STREET 2:		829 MIDDLESEX TURNPIKE
		CITY:			BILLERICA
		STATE:			MA
		ZIP:			01821
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-09-10</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000005768</issuerCik>
        <issuerName>AMERICAN SCIENCE &amp; ENGINEERING INC</issuerName>
        <issuerTradingSymbol>ASEI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001314175</rptOwnerCik>
            <rptOwnerName>Brown Denis R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O AMERICAN SCIENCE &amp; ENGINEERING,INC</rptOwnerStreet1>
            <rptOwnerStreet2>829 MIDDLESEX TURNPIKE</rptOwnerStreet2>
            <rptOwnerCity>BILLERICA</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01821</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>62.5</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-09-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>62.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2010-09-10</value>
            </exerciseDate>
            <expirationDate>
                <value>2019-09-10</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>51378</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <ownerSignature>
        <signatureName>Michelle Bielunis, Attorney-in-Fact</signatureName>
        <signatureDate>2009-09-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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