SECURITIES & EXCHANGE COMMISSION Washington, D.C. 20549 ---------------------- SCHEDULE 13GA* (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO 13d-2(b) Affiliated Managers Group, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 008252108 (CUSIP Number) December 31, 2002 (Date of event which requires filing of this statement) Check the appropriate box to designate the rule pursuant to which this Schedule 13G is filed: [ ] Rule 13d-1(b) [X] Rule 13d-1(c) [ ] Rule 13d-1(d) (Page 1 of 12 Pages) ---------------- *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page. The information required in the remainder of this cover page shall not be deemed to be "filed" for purposes of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). CUSIP No. 008252108 13GA Page 2 of 12 Pages ------------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY) Lone Spruce, L.P. ------------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP ** (a) [X] (b) [ ] ------------------------------------------------------------------------------- (3) SEC USE ONLY ------------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER -0- SHARES ---------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 28,667 OWNED BY ---------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER -0- REPORTING ---------------------------------------------------------------- PERSON WITH (8) SHARED DISPOSITIVE POWER 28,667 ------------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 28,667 ------------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ** [ ] ------------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.1% ------------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON ** PN ------------------------------------------------------------------------------- ** SEE INSTRUCTIONS BEFORE FILLING OUT! CUSIP No. 008252108 13GA Page 3 of 12 Pages ------------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY) Lone Balsam, L.P. ------------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP ** (a) [X] (b) [ ] ------------------------------------------------------------------------------- (3) SEC USE ONLY ------------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER -0- SHARES ---------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 62,911 OWNED BY ---------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER -0- REPORTING ---------------------------------------------------------------- PERSON WITH (8) SHARED DISPOSITIVE POWER 62,911 ------------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 62,911 ------------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ** [ ] ------------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.3% ------------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON ** PN ------------------------------------------------------------------------------- ** SEE INSTRUCTIONS BEFORE FILLING OUT! CUSIP No. 008252108 13GA Page 4 of 12 Pages ------------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY) Lone Sequoia, L.P. ------------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP ** (a) [X] (b) [ ] ------------------------------------------------------------------------------- (3) SEC USE ONLY ------------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER -0- SHARES ---------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 52,558 OWNED BY ---------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER -0- REPORTING ---------------------------------------------------------------- PERSON WITH (8) SHARED DISPOSITIVE POWER 52,558 ------------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 52,558 ------------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ** [ ] ------------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.2% ------------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON ** PN ------------------------------------------------------------------------------- ** SEE INSTRUCTIONS BEFORE FILLING OUT! CUSIP No. 008252108 13GA Page 5 of 12 Pages ------------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY) Lone Pine Associates LLC ------------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP ** (a) [X] (b) [ ] ------------------------------------------------------------------------------- (3) SEC USE ONLY ------------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER -0- SHARES ---------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 144,136 OWNED BY ---------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER -0- REPORTING ---------------------------------------------------------------- PERSON WITH (8) SHARED DISPOSITIVE POWER 144,136 ------------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 144,136 ------------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ** [ ] ------------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.7% ------------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON ** OO ------------------------------------------------------------------------------- ** SEE INSTRUCTIONS BEFORE FILLING OUT! CUSIP No. 008252108 13GA Page 6 of 12 Pages ------------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY) Lone Pine Capital LLC ------------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP ** (a) [X] (b) [ ] ------------------------------------------------------------------------------- (3) SEC USE ONLY ------------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER -0- SHARES ---------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 652,164 OWNED BY ---------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER -0- REPORTING ---------------------------------------------------------------- PERSON WITH (8) SHARED DISPOSITIVE POWER 652,164 ------------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 652,164 ------------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ** [ ] ------------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.0% ------------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON ** IA ------------------------------------------------------------------------------- ** SEE INSTRUCTIONS BEFORE FILLING OUT! CUSIP No. 008252108 13GA Page 7 of 12 Pages ------------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY) Stephen F. Mandel, Jr. ------------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP ** (a) [X] (b) [ ] ------------------------------------------------------------------------------- (3) SEC USE ONLY ------------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION United States ------------------------------------------------------------------------------- NUMBER OF (5) SOLE VOTING POWER -0- SHARES ---------------------------------------------------------------- BENEFICIALLY (6) SHARED VOTING POWER 796,300 OWNED BY ---------------------------------------------------------------- EACH (7) SOLE DISPOSITIVE POWER -0- REPORTING ---------------------------------------------------------------- PERSON WITH (8) SHARED DISPOSITIVE POWER 796,300 ------------------------------------------------------------------------------- (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 796,300 ------------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ** [ ] ------------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.7% ------------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON ** IN ------------------------------------------------------------------------------- ** SEE INSTRUCTIONS BEFORE FILLING OUT! CUSIP No. 008252108 13GA Page 8 of 12 Pages Item 1(a). Name of Issuer: The name of the issuer is Affiliated Managers Group, Inc. (the "Company"). Item 1(b). Address of Issuer's Principal Executive Offices: The Company's principal executive offices are located at 600 Hale Street, Prides Crossing, Massachusetts 01965. Item 2(a). Name of Person Filing: This statement is filed by: (i) Lone Spruce, L.P., a Delaware limited partnership ("Lone Spruce"), with respect to the shares of Common Stock (defined in Item 2(d) below) directly owned by it; (ii) Lone Balsam, L.P., a Delaware limited partnership ("Lone Balsam"), with respect to the shares of Common Stock directly owned by it; (iii) Lone Sequoia, L.P., a Delaware limited partnership ("Lone Sequoia"), with respect to the shares of Common Stock directly owned by it; (iv) Lone Pine Associates LLC, a Delaware limited liability company ("Lone Pine"), with respect to the shares of Common Stock directly owned by Lone Spruce, Lone Balsam and Lone Sequoia; (v) Lone Pine Capital LLC, a Delaware limited liability company ("Lone Pine Capital"), which serves as investment manager to Lone Cypress, Ltd., a Cayman Islands exempted company ("Lone Cypress"), with respect to the shares of Common Stock directly owned by Lone Cypress; (vi) Stephen F. Mandel, Jr. ("Mr. Mandel"), with respect to the shares of Common Stock directly owned by each of Lone Spruce, Lone Balsam, Lone Sequoia and Lone Cypress. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons". Any disclosures herein with respect to persons other than the Reporting Persons are made on information and belief after making inquiry to the appropriate party. Item 2(b). Address of Principal Business Office or, if None, Residence: The address of the business office of each of the Reporting Persons is Two Greenwich Plaza, Greenwich, Connecticut 06830. CUSIP No. 008252108 13GA Page 9 of 12 Pages Item 2(c). Citizenship: Lone Spruce, Lone Balsam and Lone Sequoia are limited partnerships organized under the laws of the State of Delaware. Lone Pine Associates LLC and Lone Pine Capital LLC are limited liability companies organized under the laws of the State of Delaware. Mr. Mandel is a United States citizen. Item 2(d). Title of Class of Securities: Common Stock, $0.01 par value (the "Common Stock") Item 2(e). CUSIP Number: 008252108 Item 3. If this statement is filed pursuant to Rules 13d-1(b) or 13d-2(b) or (c), check whether the person filing is a: (a) [ ] Broker or dealer registered under Section 15 of the Act, (b) [ ] Bank as defined in Section 3(a)(6) of the Act, (c) [ ] Insurance Company as defined in Section 3(a)(19) of the Act, (d) [ ] Investment Company registered under Section 8 of the Investment Company Act of 1940, (e) [ ] Investment Adviser in accordance with Rule 13d-1(b)(1)(ii)(E), (f) [ ] Employee Benefit Plan or Endowment Fund in accordance with Rule 13d-1(b)(1)(ii)(F), (g) [ ] Parent Holding Company or control person in accordance with Rule 13d-1(b)(1)(ii)(G), (h) [ ] Savings Association as defined in Section 3(b) of the Federal Deposit Insurance Act, (i) [ ] Church Plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act of 1940, (j) [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(J). If this statement is filed pursuant to Rule 13d-1(c), check the box. [X] CUSIP No. 008252108 13GA Page 10 of 12 Pages Item 4. Ownership. A. Lone Spruce, L.P. (a) Amount beneficially owned: 28,667 (b) Percent of class: 0.1% The percentages used herein and in the rest of Item 4 are calculated based upon the 21,754,520 shares of Voting Common Stock issued and outstanding as of November 11, 2002 as reported in the Company's Form 10-Q for the period ending September 30, 2002. (c)(i) Sole power to vote or direct the vote: -0- (ii) Shared power to vote or direct the vote: 28,667 (iii) Sole power to dispose or direct the disposition: -0- (iv) Shared power to dispose or direct the disposition: 28,667 B. Lone Balsam, L.P. (a) Amount beneficially owned: 62,911 (b) Percent of class: 0.3% (c)(i) Sole power to vote or direct the vote: -0- (ii) Shared power to vote or direct the vote: 62,911 (iii) Sole power to dispose or direct the disposition: -0- (iv) Shared power to dispose or direct the disposition: 62,911 C. Lone Sequoia, L.P. (a) Amount beneficially owned: 52,558 (b) Percent of class: 0.2% (c)(i) Sole power to vote or direct the vote: -0- (ii) Shared power to vote or direct the vote: 52,558 (iii) Sole power to dispose or direct the disposition: -0- (iv) Shared power to dispose or direct the disposition: 52,558 D. Lone Pine Associates LLC (a) Amount beneficially owned: 144,136 (b) Percent of class: 0.7% (c)(i) Sole power to vote or direct the vote: -0- (ii) Shared power to vote or direct the vote: 144,136 (iii) Sole power to dispose or direct the disposition: -0- (iv) Shared power to dispose or direct the disposition: 144,136 C. Lone Pine Capital LLC (a) Amount beneficially owned: 652,164 (b) Percent of class: 3.0% (c)(i) Sole power to vote or direct the vote: -0- (ii) Shared power to vote or direct the vote: 652,164 (iii) Sole power to dispose or direct the disposition: -0- (iv) Shared power to dispose or direct the disposition: 652,164 CUSIP No. 008252108 13GA Page 11 of 12 Pages D. Stephen F. Mandel, Jr. (a) Amount beneficially owned: 796,300 (b) Percent of class: 3.7% (c)(i) Sole power to vote or direct the vote: -0- (ii) Shared power to vote or direct the vote: 796,300 (iii) Sole power to dispose or direct the disposition: -0- (iv) Shared power to dispose or direct the disposition: 796,300 Item 5. Ownership of Five Percent or Less of a Class. If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following [x]. Item 6. Ownership of More than Five Percent on Behalf of Another Person. Not applicable. Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company. Not applicable. Item 8. Identification and Classification of Members of the Group. See Item 2. Item 9. Notice of Dissolution of Group. Not applicable. Item 10. Certification. Each of the Reporting Persons hereby makes the following certification: By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. CUSIP No. 008252108 13GA Page 12 of 12 Pages SIGNATURES After reasonable inquiry and to the best of our knowledge and belief, the undersigned certify that the information set forth in this statement is true, complete and correct. DATED: February 13, 2003 LONE SPRUCE, L.P. By: Lone Pine Associates LLC, General Partner By: /s/ Stephen F. Mandel, Jr. -------------------------- Stephen F. Mandel, Jr. Managing Member LONE BALSAM, L.P. By: Lone Pine Associates LLC, General Partner By: /s/ Stephen F. Mandel, Jr. -------------------------- Stephen F. Mandel, Jr. Managing Member LONE SEQUOIA, L.P. By: Lone Pine Associates LLC, General Partner By: /s/ Stephen F. Mandel, Jr. -------------------------- Stephen F. Mandel, Jr. Managing Member LONE PINE ASSOCIATES LLC By: /s/ Stephen F. Mandel, Jr. -------------------------- Stephen F. Mandel, Jr. Managing Member LONE PINE CAPITAL LLC By: /s/ Stephen F. Mandel, Jr. -------------------------- Stephen F. Mandel, Jr. Managing Member STEPHEN F. MANDEL, JR. /s/ Stephen F. Mandel, Jr. -------------------------------