Ownership Submission
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
OMB APPROVAL
OMB Number: 3235-0287
Expires: January 31, 2005
Estimated average burden hours per response... 0.5

(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)
01/01/2012
(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 01/01/2012   M   719,615 A $ 7.8333 1,091,660 D  
Common Shares, $.0033 par value per share 01/01/2012   F   151,403 (3) D $ 37.23 940,257 D  
Common Shares, $.0033 par value per share 01/01/2012   M   480,385 A $ 7.8333 480,385 I By 2005 GRAT
Common Shares, $.0033 par value per share 01/01/2012   F   101,071 (4) D $ 37.23 379,314 I By 2005 GRAT
Common Shares, $.0033 par value per share               116,613 I By Limited Liability Company
Series B Non-Cumulative Preferred Shares (non-convertible)               67,273.3862 I By 2010 GRAT
Series A Non-Cumulative Preferred Shares (non-convertible)               11,224.4855 I By 2010 GRAT
Series B Non-Cumulative Preferred Shares (non-convertible)               1,400 I By spouse
Common Shares, $.0033 par value per share               11,616 I By child

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number. SEC 1474 (9-02)

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) $ 7.8333               (1) 01/01/2012 Common Shares, $.0033 par value per share 719,615 (2)   719,615 D  
Stock Option (right to buy) $ 7.8333               (1) 01/01/2012 Common Shares, $.0033 par value per share 480,385   480,385 I By 2005 GRAT
Stock Option (right to buy) $ 7.8333 01/01/2012   M     719,615   (1) 01/01/2012 Common Shares, $.0033 par value per share 719,615 $ 0 0 D  
Stock Option (right to buy) $ 7.8333 01/01/2012   M     480,385   (1) 01/01/2012 Common Shares, $.0033 par value per share 480,385 $ 0 0 I By 2005 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/ Louis T. Petrillo, Attorney in fact   01/03/2012
**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 stock option became exercisable in three equal annual installments with the first installment being exercisable on January 1, 2002 and the second and third installments being exercisable on Jaunuary 1, 2003 and January 1, 2004.
(2) 167,258 of the 719,615 stock options were previously reported as indirectly owned by the 2005 GRAT; on December 21, 2011, the 2005 GRAT distributed 167,258 of such stock options to the reporting person and as a result, the reporting person directly owns 719,615 stock options.
(3) On January 1, 2012, the reporting person exercised 719,615 stock options and, under the net settlement provisions of the applicale stock option agreement, 151,403 common shares were withheld in payment of the exercise price.
(4) On January 1, 2012, the reporting person's 2005 GRAT exercised 480,385 stock options and, under the net settlement provisions of the applicale stock option agreement, 101,071 common shares were withheld in payment of the exercise price.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.