ARCH CAPITAL GROUP LTD. — Director's Dealing 2010

May 7, 2010

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: ARCH CAPITAL GROUP LTD. (ACGL)
CIK: 0000947484
Period of Report: 2010-05-05

Reporting Person: PETRILLO LOUIS T (Officer of Subsidiary)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-05-05	Common Shares, $.01 par value per share	A	5000	—	Acquired	29010	Direct
2010-05-06	Common Shares, $.01 par value per share	F	569	—	Disposed	28441	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-05-05	Stock Appreciation Right	$75.03	A	5000	Acquired	2020-05-05	Common Shares, $.01 par value per share (5000)	Direct

Footnotes

F1: Represents restricted shares that vest in three equal annual installments on May 5th in each of 2011, 2012 and 2013, subject to the applicable award agreement.

F2: The stock appreciation right will become exercisable in three equal annual installments, with the first installment becoming exercisable on May 5, 2011 and the next two installments on May 5, 2012 and May 5, 2013, subject to the applicable award agreement.

F3: Represents shares withheld to pay taxes due upon the vesting of restricted stock.