------------------------ OMB APPROVAL ------------------------ OMB Number: 3235-0145 Expires: 30-Sep-03 Estimated Average burden hours per reponse ------------------------ UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 (AMENDMENT NO. _________)* NetScout Systems, Inc. -------------------------------------------------------------------------------- (Name of Issuer) Common Stock Par Value $.01 -------------------------------------------------------------------------------- (Title of Class of Securities) 64115T 10 4 -------------------------------------------------------------------------------- (CUSIP Number) Check the following box if a fee is being paid with this statement [ ]. (A fee is not required only if the filing person: (1) has a previous statement on file reporting beneficial ownership of more than five percent of the class of securities described in Item 1; and (2) has filed no amendment subsequent thereto reporting beneficial ownership of five percent or less of such class.) (See Rule 13d-7). *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 the purpose 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). SEC 1745 (10-88) Page 1 CUSIP NO. 64115T 10 4 13G PAGE 2 1 NAME OF REPORTING PERSON S.S. OR I.R.S IDENTIFICATION NO. OF ABOVE PERSON TA/Advent VIII L.P. 04-3334380 Advent Atlantic & Pacific III L.P. 04-3299318 TA Executives Fund LLC 04-3398534 TA Investors LLC 04-3395404 TA Associates VIII LLC 04 3334378 High Street Partners L.P. 04-3295365 TA Associates, Inc. 04-3205751 2 CHECK THE BOX IF A MEMBER OF A GROUP* (a) /X/ (b) / / 3 SEC USE ONLY 4 CITIZENSHIP OR PLACE OF ORGANIZATION TA/Advent VIII L.P. Delaware Advent Atlantic & Pacific III L.P. Delaware TA Executives Fund LLC Delaware TA Investors LLC Delaware TA Associates VIII Delaware High Street Partners L.P. Massachusetts TA Associates, Inc. Delaware 5 SOLE VOTING POWER NUMBER OF TA/Advent VIII L.P. 3,798,950 Advent Atlantic & Pacific III L.P. 993,561 TA Executives Fund LLC 100,680 SHARES TA Investors LLC 105,979 TA Associates VIII LLC 0 High Street Partners L.P. 26,837 TA Associates, Inc. 1,008 6 SHARED VOTING POWER BENEFICIALLY N/A OWNED BY 7 SOLE DISPOSITIVE POWER EACH TA/Advent VIII L.P. 3,798,950 REPORTING Advent Atlantic & Pacific III L.P. 993,561 TA Executives Fund LLC 100,680 TA Investors LLC 105,979 TA Associates VIII LLC 0 High Street Partners L.P. 26,837 TA Associates, Inc. 1,008 8 SHARED DISPOSITIVE POWER WITH N/A 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON TA/Advent VIII L.P. 3,798,950 Advent Atlantic & Pacific III L.P. 993,561 TA Executives Fund LLC 100,680 TA Investors LLC 105,979 TA Associates VIII LLC 0 High Street Partners L.P. 26,837 TA Associates, Inc. 1,008 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 TA/Advent VIII L.P. 12.68% Advent Atlantic & Pacific III L.P. 3.32% TA Executives Fund LLC 0.34% TA Investors LLC 0.35% TA Associates VIII LLC 0.00% High Street Partners L.P. 0.09% TA Associates, Inc. 0.00% 12 TYPE OF REPORTING PERSON Three Limited Partnerships Three Limited Liability Companies One Corporation SEE INSTRUCTION BEFORE FILLING OUT! ATTACHMENT TO FORM 13G PAGE 3 ITEM 1 (a) NAME OF ISSUER: NetScout Systems, Inc. ITEM 1 (b) ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES: 4 Technology Park Drive Westford, MA 01886 ITEM 2 (a) NAME OF PERSON FILING: TA/Advent VIII L.P. Advent Atlantic & Pacific III L.P. TA Executives Fund LLC TA Investors LLC. TA Associates VIII LLC High Street Partners L.P. TA Associates, Inc. ITEM 2 (b) ADDRESS OF PRINCIPAL BUSINESS OFFICE: c/o TA Associates 125 High Street, Suite 2500 Boston, MA 02110 ITEM 2 (c) CITIZENSHIP: Not Applicable ITEM 2 (d) TITLE AND CLASS OF SECURITIES: Common ITEM 2 (e) CUSIP NUMBER: 64115T 10 4 ITEM 3 IF THIS STATEMENT IS FILED PURSUANT TO RULES 13d-1 (b) OR 13d-2 (b), CHECK WHETHER THE PERSON FILING IS A: Not Applicable ITEM 4 OWNERSHIP ITEM 4 (a) AMOUNT BENEFICIALLY OWNED: COMMON STOCK ------------ TA/Advent VIII L.P. 3,798,950 Advent Atlantic & Pacific III L.P. 993,561 TA Executives Fund LLC 100,680 TA Investors LLC 105,979 TA Associates VIII LLC 0 High Street Partners L.P. 26,837 TA Associates, Inc. 1,008 ITEM 4 (b) PERCENT OF CLASS PERCENTAGE ---------- TA/Advent VIII L.P. 12.68% Advent Atlantic & Pacific III L.P 3.32% TA Executives Fund LLC 0.34% TA Investors LLC 0.35% TA Associates VIII LLC 0.00% High Street Partners L.P. 0.09% TA Associates, Inc. 0.00% ITEM 4 (c) NUMBER OF SHARES AS TO WHICH SUCH PERSON HAS: (I) SOLE POWER TO VOTE OR DIRECT THE VOTE: COMMON STOCK TA/Advent VIII L.P. 3,798,950 Advent Atlantic & Pacific III L.P 993,561 TA Executives Fund LLC 100,680 TA Investors LLC 105,979 TA Associates VIII LLC 0 High Street Partners L.P. 26,837 TA Associates, Inc. 1,008 (II) SHARED POWER TO VOTE OR DIRECT THE VOTE: N/A (III) SOLE POWER TO DISPOSE OR DIRECT THE DISPOSITION: COMMON STOCK TA/Advent VIII L.P. 3,798,950 Advent Atlantic & Pacific III L.P 993,561 TA Executives Fund LLC 100,680 TA Investors LLC 105,979 TA Associates VIII LLC 0 High Street Partners L.P. 26,837 TA Associates, Inc. 1,008 (IV) SHARED POWER TO DISPOSE OR DIRECT THE DISPOSITION N/A PAGE 4 ITEM 5 OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS: Not Applicable ITEM 6 OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON: Not Applicable ITEM 7 IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY THAT ACQUIRED . THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY: Not Applicable ITEM 8 IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP: This schedule 13G is filed pursuant to Rule 13d-1 (c). For the agreement of group members to a joint filing, see below. ITEM 9 NOTICE OF DISSOLUTION OF GROUP: Not Applicable ITEM 10 CERTIFICATION: Not Applicable SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. ------------------------- Date /s/ Thomas P. Alber ------------------------- Signature Chief Financial Officer ------------------------- Name/Title AGREEMENT FOR JOINT FILING TA/Advent VIII L.P., Advent Atlantic and Pacific III L.P., TA Associates VIII LLC,TA Executives Fund LLC, High Street Partners L.P., TA Associates, Inc. and TA Investors LLC, hereby agree that TA Associates shall file with the Securities and Exchange Commission a joint schedule 13G on behalf of the above-named parties concerning their beneficial ownership of NetScout Systems, Inc. Dated: TA/ADVENT VIII L.P. By: TA Associates VIII LLC, its General Partner By: TA Associates, Inc. its Manager By: Thomas P. Alber, Chief Financial Officer ADVENT ATLANTIC & PACIFIC III L.P. By: TA Associates AAP III Partners L.P., its General Partner By: TA Associates, Inc. its General Partner By: Thomas P. Alber, Chief Financial Officer TA EXECUTIVES FUND LLC By: TA Associates, Inc., its Manager By: Thomas P. Alber, Chief Financial Officer TA INVESTORS LLC By: TA Associates, Inc., its Manager By: Thomas P. Alber, Chief Financial Officer TA Associates VIII LLC By: TA Associates, Inc., its Manager By: -------------------------------------------- Thomas P. Alber, Chief Financial Officer TA Associates, Inc. By: -------------------------------------------- Thomas P. Alber, Chief Financial Officer High Street Partners L.P. By: -------------------------------------------- Thomas P. Alber, General Partner