-----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,
 MtprRimgSf47BVnZGwKYhDpDIrmxpEbc1Rg8rmg/O2zH6KAJG/zf4KMTCBxGPcYf
 A/crhlJhxP5EZspIHMkSWQ==

<SEC-DOCUMENT>0001179110-08-018860.txt : 20081103
<SEC-HEADER>0001179110-08-018860.hdr.sgml : 20081103
<ACCEPTANCE-DATETIME>20081103144507
ACCESSION NUMBER:		0001179110-08-018860
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20081031
FILED AS OF DATE:		20081103
DATE AS OF CHANGE:		20081103

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ARCH CAPITAL GROUP LTD.
		CENTRAL INDEX KEY:			0000947484
		STANDARD INDUSTRIAL CLASSIFICATION:	FIRE, MARINE & CASUALTY INSURANCE [6331]
		IRS NUMBER:				000000000
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		WESSEX HOUSE
		STREET 2:		45 REID STREET
		CITY:			HAMILTON
		STATE:			D0
		ZIP:			HM 12
		BUSINESS PHONE:		441-278-9250

	MAIL ADDRESS:	
		STREET 1:		WESSEX HOUSE
		STREET 2:		45 REID STREET
		CITY:			HAMILTON
		STATE:			D0
		ZIP:			HM 12

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ARCH CAPITAL GROUP LTD
		DATE OF NAME CHANGE:	20000508

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	RISK CAPITAL HOLDINGS INC
		DATE OF NAME CHANGE:	19950816

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	RISK CAPITAL RE INC
		DATE OF NAME CHANGE:	19950703

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Vollaro John D
		CENTRAL INDEX KEY:			0001304230

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-16209
		FILM NUMBER:		081157146

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		441-278-9250

	MAIL ADDRESS:	
		STREET 1:		WESSEX HOUSE 3RD FLOOR
		STREET 2:		45 REID STREET
		CITY:			HAMILTON
		STATE:			D0
		ZIP:			HM12
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-10-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000947484</issuerCik>
        <issuerName>ARCH CAPITAL GROUP LTD.</issuerName>
        <issuerTradingSymbol>ACGL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001304230</rptOwnerCik>
            <rptOwnerName>Vollaro John D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>WESSEX HOUSE, 4TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2>45 REID STREET</rptOwnerStreet2>
            <rptOwnerCity>HAMILTON</rptOwnerCity>
            <rptOwnerState>D0</rptOwnerState>
            <rptOwnerZipCode>HM12</rptOwnerZipCode>
            <rptOwnerStateDescription>BERMUDA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP, CFO and Treasurer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares, $.01 par value per share</value>
            </securityTitle>
            <transactionDate>
                <value>2008-10-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>85000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.30</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>128900</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares, $.01 par value per share</value>
            </securityTitle>
            <transactionDate>
                <value>2008-10-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2300</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>68.96</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>126600</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares, $.01 par value per share</value>
            </securityTitle>
            <transactionDate>
                <value>2008-10-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>82700</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>69.25</value>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>43900</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>25.30</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-10-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>85000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2012-01-18</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares, $.01 par value per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>85000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The options became exercisable in three equal annual installments, with the first installment becoming exercisable on January 18, 2002 and the next two installments on January 18, 2003 and January 18, 2004, subject to the applicable award agreement.</footnote>
        <footnote id="F2">Represents a weighted average sale price; the sales prices ranged from $68.92 to $68.995.  Upon request, the full sale information regarding the number of shares sold at each price increment will be provided to the Commission, the issuer or a security holder of the issuer.</footnote>
        <footnote id="F3">Represents a weighted average sale price; the sales prices ranged from $69.00 to $69.72.  Upon request, the full sale information regarding the number of shares sold at each price increment will be provided to the Commission, the issuer or a security holder of the issuer.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ John D. Vollaro</signatureName>
        <signatureDate>2008-11-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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