8-K

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C.  20549

FORM 8-K

Current Report Pursuant to Section 13 or 15(d)
of the Securities Exchange Act of 1934

March 22, 2010Date of Report (Date of earliest event reported)

Arch Capital Group Ltd.

(Exact name of registrant as specified in its charter)

Bermuda	0-26456	N/A
(State or other jurisdiction of incorporation or organization)	(Commission File Number)	(I.R.S. Employer Identification No.)

Wessex House, 45 Reid Street, Hamilton HM 12, Bermuda(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code:  (441) 278-9250

N/A(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

oWritten communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

oSoliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

oPre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

oPre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

ITEM 7.01           Regulation FD Disclosure.

On March 22, 2010, Arch Capital Group Ltd. issued a press release announcing initial estimates of impact from the Chilean earthquake, European Windstorm Xynthia and Australian hailstorms and floods.  A copy of this press release is attached to this Current Report on Form 8-K as Exhibit 99.1 and is incorporated herein by reference.

The information in this Current Report on Form 8-K, including the information set forth in Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

ITEM 9.01           Financial Statements and Exhibits.

EXHIBIT NO.	DESCRIPTION
99.1	Press Release dated March 22, 2010 announcing initial estimates of impact from the Chilean earthquake, European Windstorm Xynthia and Australian hailstorms and floods.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	ARCH CAPITAL GROUP LTD.
Date: March 22, 2010	By:	/s/ John C.R. Hele
		Name:	John C.R. Hele
		Title:	Executive Vice President, Chief Financial Officer & Treasurer

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EXHIBIT INDEX

EXHIBIT NO.	DESCRIPTION
99.1	Press Release dated March 22, 2010 announcing initial estimates of impact from the Chilean earthquake, European Windstorm Xynthia and Australian hailstorms and floods.

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EX-99.1

Exhibit 99.1

ARCH CAPITAL GROUP LTD.ANNOUNCES INITIAL ESTIMATES OF IMPACT FROMCHILEAN EARTHQUAKE, EUROPEAN WINDSTORM XYNTHIA ANDAUSTRALIAN HAILSTORMS AND FLOODS

HAMILTON, BERMUDA, MARCH 22, 2010 —  Arch Capital Group Ltd. [Nasdaq: ACGL] today announced that it expects pre-tax earnings for the 2010 first quarter to be negatively impacted by the effects of the Chilean earthquake in the range of $35 million to $50 million, net of reinsurance, retrocessions and reinstatement premiums.  This preliminary net loss estimate for the Chilean earthquake is based on projected industry insured losses of $6 billion to $8 billion.

In addition, the Company announced that it expects pre-tax earnings for the 2010 first quarter to be negatively impacted by the combined effects of European Windstorm Xynthia and the Australian hailstorms and floods in an aggregate amount of less than $15 million, net of reinsurance, retrocessions and reinstatement premiums.  This preliminary net loss estimate is based on projected industry insured losses of $2 billion to $4 billion for European Windstorm Xynthia and approximately $1 billion for the Australian hailstorms and floods.

The above initial loss estimates are based on currently available information derived from modeling techniques, current industry assessments of exposure, preliminary claims information obtained from the Company’s clients and brokers to date and a review of the Company’s in-force contracts.  The Company’s actual losses from these events may vary materially from the estimates due to the inherent uncertainties in making such determinations resulting from several factors, including the preliminary nature of the available information, the potential inaccuracies and inadequacies in the data provided by clients and brokers, the modeling techniques and the application of such techniques, the contingent nature of business interruption exposures, the effects of any resultant demand surge on claims activity and attendant coverage issues.  In addition, there is uncertainty regarding total losses for the insurance industry for these events, particularly with respect to the Chilean earthquake.  Actual losses may also increase if the Company’s reinsurers fail to meet their obligations to the Company or the reinsurance protections purchased by the Company are exhausted or are otherwise unavailable.

Arch Capital Group Ltd., a Bermuda-based company with approximately $4.7 billion in capital at December 31, 2009, provides insurance and reinsurance on a worldwide basis through its wholly owned subsidiaries.

Cautionary Note Regarding Forward-Looking Statements

The Private Securities Litigation Reform Act of 1995 provides a “safe harbor” for forward-looking statements. This release or any other written or oral statements made by or on behalf of Arch Capital Group Ltd. and its subsidiaries may include forward-looking statements, which reflect our current views with respect to future events and financial performance. All statements other than statements of historical fact included in or incorporated by reference in this release are forward-looking statements.

Forward-looking statements can generally be identified by the use of forward-looking terminology such as “may,” “will,” “expect,” “intend,” “estimate,” “anticipate,” “believe” or “continue” or their negative or variations or similar terminology. Forward-looking statements involve our current assessment of risks and uncertainties. Actual events and results may differ materially from those expressed or implied in these statements. A non-exclusive list of the important factors that could cause actual results to differ materially from those in such forward-looking statements includes the following: adverse general economic and market conditions; increased competition; pricing and policy term trends; fluctuations in the actions of rating agencies and our ability to maintain and improve our ratings; investment performance; the loss of key personnel; the adequacy of our loss reserves, severity and/or frequency of losses, greater than expected loss ratios and adverse development on claim and/or claim expense liabilities; greater frequency or severity of unpredictable natural and man-made catastrophic events; the impact of acts of terrorism and acts of war; changes in regulations and/or tax laws in the United States or elsewhere; our ability to successfully integrate, establish and maintain operating procedures as well as integrate the businesses we have acquired or may acquire into the existing operations; changes in accounting principles or policies; material differences between actual and expected assessments for guaranty funds and mandatory pooling arrangements; availability and cost to us of reinsurance to manage our gross and net exposures; the failure of others to meet their obligations to

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us; and other factors identified in our filings with the U.S. Securities and Exchange Commission.

The foregoing review of important factors should not be construed as exhaustive and should be read in conjunction with other cautionary statements that are included herein or elsewhere. All subsequent written and oral forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by these cautionary statements. We undertake no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events or otherwise.

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Contact:	Arch Capital Group Ltd.
	John C.R. Hele
	(441) 278-9250

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