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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 AZ5HEM93bJR5XDFKOMEdrlu7Cudm/aSWBOfggLyRtSVCjtuoyTL/GOuj+zb0BWh4
 9utT4ShNy/tFNDq06FN/ug==

<SEC-DOCUMENT>0001246360-10-001507.txt : 20100312
<SEC-HEADER>0001246360-10-001507.hdr.sgml : 20100312
<ACCEPTANCE-DATETIME>20100312165610
ACCESSION NUMBER:		0001246360-10-001507
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100310
FILED AS OF DATE:		20100312
DATE AS OF CHANGE:		20100312

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Weld Gwen E
		CENTRAL INDEX KEY:			0001378831

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-33196
		FILM NUMBER:		10678406

	MAIL ADDRESS:	
		STREET 1:		C/O ISILON SYSTEMS, INC.
		STREET 2:		3101 WESTERN AVENUE
		CITY:			SEATTLE
		STATE:			WA
		ZIP:			98121

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Isilon Systems, Inc.
		CENTRAL INDEX KEY:			0001373671
		STANDARD INDUSTRIAL CLASSIFICATION:	COMPUTER STORAGE DEVICES [3572]
		IRS NUMBER:				912101027
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		3101 WESTERN AVENUE
		CITY:			SEATTLE
		STATE:			WA
		ZIP:			98121
		BUSINESS PHONE:		206-315-7500

	MAIL ADDRESS:	
		STREET 1:		3101 WESTERN AVENUE
		CITY:			SEATTLE
		STATE:			WA
		ZIP:			98121
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-03-10</periodOfReport>

    <notSubjectToSection16>false</notSubjectToSection16>

    <issuer>
        <issuerCik>0001373671</issuerCik>
        <issuerName>Isilon Systems, Inc.</issuerName>
        <issuerTradingSymbol>ISLN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001378831</rptOwnerCik>
            <rptOwnerName>Weld Gwen E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3101 WESTERN AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SEATTLE</rptOwnerCity>
            <rptOwnerState>WA</rptOwnerState>
            <rptOwnerZipCode>98121</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>VP HR and Organizational Dev</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-03-10</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6000</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.8528</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>148516</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The sales reported by Ms. Weld were effected pursuant to a Rule 10b5-1 trading plan adopted on November 1, 2009.</footnote>
        <footnote id="F2">The &quot;Amount&quot; and &quot;Price&quot; reported in this Column 4 reflect the aggregate number and weighted-average price, respectively, of shares disposed. These shares were sold in multiple transactions at prices ranging from $8.83 to $8.90, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the SEC staff, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth herein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Keenan Conder, Attorney-in-Fact</signatureName>
        <signatureDate>2010-03-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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