-----BEGIN PRIVACY-ENHANCED MESSAGE-----
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,
 PuVNBax/DKQLVFink1Ynbw2DScOJvxkUl13oYoSubScr8mpmHPhyK9IuwTPzu+ed
 trszLr92L5Q6xwc0j++x5Q==

<SEC-DOCUMENT>0001331392-08-000009.txt : 20080320
<SEC-HEADER>0001331392-08-000009.hdr.sgml : 20080320
<ACCEPTANCE-DATETIME>20080320082920
ACCESSION NUMBER:		0001331392-08-000009
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080317
FILED AS OF DATE:		20080320
DATE AS OF CHANGE:		20080320

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Lyne Daniel J
		CENTRAL INDEX KEY:			0001331392

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-25705
		FILM NUMBER:		08700726

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		978-439-5511

	MAIL ADDRESS:	
		STREET 1:		GSI GROUP INC
		STREET 2:		39 MANNING ROAD
		CITY:			BILLERICA
		STATE:			MA
		ZIP:			01821

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			GSI GROUP INC
		CENTRAL INDEX KEY:			0001076930
		STANDARD INDUSTRIAL CLASSIFICATION:	MISCELLANEOUS ELECTRICAL MACHINERY, EQUIPMENT & SUPPLIES [3690]
		IRS NUMBER:				980110412
		STATE OF INCORPORATION:			A3
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		39 MANNING ROAD
		STREET 2:		.
		CITY:			BILLERICA
		STATE:			MA
		ZIP:			01821
		BUSINESS PHONE:		978-439-5511

	MAIL ADDRESS:	
		STREET 1:		39 MANNING ROAD
		STREET 2:		.
		CITY:			BILLERICA
		STATE:			MA
		ZIP:			01821

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	GSI LUMONICS INC
		DATE OF NAME CHANGE:	19990401

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	GSI LUMONICS
		DATE OF NAME CHANGE:	19990331

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	LUMONICS INC
		DATE OF NAME CHANGE:	19990115
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2008-03-17</periodOfReport>

    <dateOfOriginalSubmission>2008-03-19</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001076930</issuerCik>
        <issuerName>GSI GROUP INC</issuerName>
        <issuerTradingSymbol>GSIG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001331392</rptOwnerCik>
            <rptOwnerName>Lyne Daniel J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>GSI GROUP INC</rptOwnerStreet1>
            <rptOwnerStreet2>39 MANNING ROAD</rptOwnerStreet2>
            <rptOwnerCity>BILLERICA</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01821</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-03-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>29750</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>114710</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">12,500 time based vest in three equal annual installments beginning on March 26, 2009.  17,250 performance based vest in acordance with performance target for fiscal year 2008 in three equal annual installments beginning on March 26, 2009.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Daniel J. Lyne</signatureName>
        <signatureDate>2008-03-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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