FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * IORDANOU CONSTANTINE   2. Issuer Name and Ticker or Trading Symbol ARCH CAPITAL GROUP LTD. [ACGL] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Chairman, President & CEO (Last) (First) (Middle) WESSEX HOUSE, 5TH FLOOR, 45 REID STREET 3. Date of Earliest Transaction (Month/Day/Year) 08/29/2011 (Street) HAMILTON, D0 HM 12 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Shares, $.0033 par value per share 08/29/2011   S   70,000 (6) D $ 33.9069 (5) 422,045 (4) D   Common Shares, $.0033 par value per share               343,245 (4) I By Limited Liability Company (1) Series B Non-Cumulative Preferred Shares (non-convertible)               67,273.3862 I By GRAT Series A Non-Cumulative Preferred Shares (non-convertible)               11,224.4855 I BY GRAT Series B Non-Cumulative Preferred Shares (non-convertible)               1,400 I By spouse Common Shares, $.0033 par value per share               23,232 (4) I By children

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Stock Option (right to buy)

$ 18.757

(2)

02/23/2016

Common Shares, $.0033 par value per share

132,447 (3) (4)

132,447 (4)

D

Stock Option (right to buy)

$ 18.757

(2)

02/23/2016

Common Shares, $.0033 par value per share

317,553 (4)

317,553 (4)

I

By GRAT

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
IORDANOU CONSTANTINE WESSEX HOUSE, 5TH FLOOR 45 REID STREET HAMILTON, D0 HM 12	X		Chairman, President & CEO

Signatures

/s/ Constantine Iordanou		08/30/2011
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	The shares are owned by Mathiatis LLC, a limited liability company. The reporting person owns all of the membership interests in Mathiatis LLC and serves as its sole managing member.
(2)	The stock option became exercisable in three equal annual installments with the first installment being exercisable on February 23, 2007 and the second and third installments being exercisable on February 23, 2008 and February 23, 2009.
(3)	On June 9, 2011, 132,447 stock options were distributed from a GRAT. Such options were previously reported as indirectly beneficially held by a GRAT. Following such distribution, the reporting person owns 132,447 stock options directly and 317,553 stock options indirectly by the GRAT.
(4)	The amount of common shares includes common shares acquired in connection with a 3-for-1 share split effectuated on May 11, 2011.
(5)	Represents a weighted average sales price; the sales prices range from $33.85 to $33.9501. Upon request, the full sale information regarding the number of shares sold at each price increment will be provided to the Commission or to a security holder of the issuer.
(6)	The shares were sold in order to satisfy state and federal income tax obligations.

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