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 * SHATTUCK MAYO A III   2. Issuer Name and Ticker or Trading Symbol CONSTELLATION ENERGY GROUP INC [CEG] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Chairman, Pres. & CEO CEG (Last) (First) (Middle) 750 E. PRATT STREET 3. Date of Earliest Transaction (Month/Day/Year) 12/21/2005 (Street) BALTIMORE, MD 21202 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 Stock 12/21/2005   M   1,375,000 (1) A $ 27.93 1,540,576 D   Common Stock 12/21/2005   M   92,387 (1) A $ 39.63 1,632,963 D   Common Stock 12/21/2005   F   1,051,361 (2) D $ 58.33 583,964 (3) D   Common Stock               549.6255 (4) I By 401(k) Plan

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 Options (right to buy) (5)

$ 27.93

12/21/2005

M

1,375,000 (1)

(6)

02/05/2012

Common Stock

1,375,000

$ 0

0

D

Stock Options (right to buy) (5)

$ 58.33

12/21/2005

A

975,487 (7)

12/21/2005

02/05/2012

Common Stock

975,487

$ 0

975,487

D

Stock Options (right to buy) (5)

$ 39.63

12/21/2005

M

92,387 (1)

(8)

02/26/2014

Common Stock

92,387

$ 0

184,773

D

Stock Options (right to buy) (5)

$ 58.33

12/21/2005

A

75,874 (7)

12/21/2005

02/26/2014

Common Stock

75,874

$ 0

75,874

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
SHATTUCK MAYO A III 750 E. PRATT STREET BALTIMORE, MD 21202	X		Chairman, Pres. & CEO CEG

Signatures

Charles A. Berardesco, Attorney-In-Fact		12/22/2005
**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)	At the request of the issuer, the officer has exercised all vested options held by such officer for purposes of minimizing the amount of excise taxes and tax gross-up payable by the issuer on behalf of the officer pursuant to Section 4999 of the Internal Revenue Code.
(2)	Shares were withheld to pay exercise prices and taxes due on the total of 1,467,387 stock options exercised on 12/21/05.
(3)	This amount includes shares obtained through reinvested dividends since the Form 4 filed on 2/28/05.
(4)	This amount includes 84.4815 shares acquired since the Form 4 filed on 2/28/05.
(5)	These are employee stock options.
(6)	Options vested on 2/5/03, 2/5/04, 2/5/05, and 12/16/05.
(7)	Represents replacement options granted to the officer following exercise of existing vested options on 12/21/05. The aggregate number of replacement options received is equal to the total number of options exercised less the actual shares received by the officer upon exercise of the options.
(8)	Options vest in three installments beginning on 2/26/05. The second and third installments will vest on 2/26/06 and 2/26/07, respectively.

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