ARCH CAPITAL GROUP LTD. — Director's Dealing 2010

Sep 10, 2010

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: ARCH CAPITAL GROUP LTD. (ACGL)
CIK: 0000947484
Period of Report: 2010-09-08

Reporting Person: Lyons Mark Donald (Chairman & CEO Arch Insur Gr)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-09-08	Common Shares, $.01 par value per share	S	2500	$80.8482	Disposed	52403	Direct

Footnotes

F1: 23,950 of such amount will settle in Issuer's common shares upon the termination of the Reporting Person's employment, as specifically provided in the award agreements.

F2: Represents a weighted average sale price; the sale prices ranged from $80.83 to $80.9018. Upon request, the full sale information regarding the number of shares sold at each price increment will be provided to the Commission or a security holder of the issuer.