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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 IBnP42zPnCu68DY0nD2CoKv+3IGvYdySUTGpzRxk/OFN70aSTzV//EDa9aBMkDv9
 7N/1/i/Uq/94sigr6SIZjQ==

<SEC-DOCUMENT>0001246151-04-000006.txt : 20040113
<SEC-HEADER>0001246151-04-000006.hdr.sgml : 20040113
<ACCEPTANCE-DATETIME>20040113202800
ACCESSION NUMBER:		0001246151-04-000006
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040106
FILED AS OF DATE:		20040113

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			GAITHER JAMES C
		CENTRAL INDEX KEY:			0001199037

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-20725
		FILM NUMBER:		04523751

	BUSINESS ADDRESS:	
		STREET 1:		NVIDIA CORP.
		STREET 2:		2701 SAN TOMAS EXPRESSWAY
		CITY:			SANTA CLARA
		STATE:			CA
		ZIP:			95050

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SIEBEL SYSTEMS INC
		CENTRAL INDEX KEY:			0001006835
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		IRS NUMBER:				943187233
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2207 BRIDGEPOINTE PARKWAY
		CITY:			SAN MATEO
		STATE:			CA
		ZIP:			94404
		BUSINESS PHONE:		6504775000

	MAIL ADDRESS:	
		STREET 1:		2207 BRIDGEPOINTE PARKWAY
		CITY:			SAN MATEO
		STATE:			CA
		ZIP:			94404
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001199037d20040113f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<ownershipDocument><schemaVersion>X0201</schemaVersion>    <documentType>4</documentType><periodOfReport>2004-01-06</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0001006835</issuerCik><issuerName>SIEBEL SYSTEMS INC</issuerName>        <issuerTradingSymbol>SEBL</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001199037</rptOwnerCik><rptOwnerName>GAITHER JAMES C</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>C/O SUTTER HILL VENTURES</rptOwnerStreet1><rptOwnerStreet2>755 PAGE MILL ROAD</rptOwnerStreet2><rptOwnerCity>PALO ALTO</rptOwnerCity><rptOwnerState>CA</rptOwnerState><rptOwnerZipCode>94304</rptOwnerZipCode><rptOwnerStateDescription></rptOwnerStateDescription></reportingOwnerAddress><reportingOwnerRelationship><isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle></officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><n
onDerivativeTable></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Stock Options (Right to buy)</value></securityTitle><conversionOrExercisePrice><value>15.39</value></conversionOrExercisePrice><transactionDate><value>2004-01-06</value></transactionDate><deemedExecutionDate></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>20000</value></transactionShares><transactionPricePerShare><value>0</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2005-01-06</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>2010-01-05</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>20000</value></
underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>20000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">The options becomes exercisable at a rate of 20% on January 6, 2005 and 5% each quarter of service thereafter.</footnote></footnotes><ownerSignature><signatureName>James C. Gaither</signatureName><signatureDate>2004-01-13</signatureDate></ownerSignature></ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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