CUSIP No. 36229U102                 13D/A                   Page 1 of 7


                        SECURITIES & EXCHANGE COMMISSION
                             Washington, D.C. 20549
                             ----------------------

                                 SCHEDULE 13D/A*

                                (Amendment No. 4)

                                 GSI GROUP INC.
             ------------------------------------------------------
                                (Name of Issuer)

                                  COMMON STOCK
             ------------------------------------------------------
                         (Title of Class of Securities))

                                    36229U102
             ------------------------------------------------------
                                 (CUSIP NUMBER)

                                   John Oliva
                       Highbridge Capital Management, LLC
                         9 West 57th Street, 27th Floor
                            New York, New York 10019
             ------------------------------------------------------
                  (Name, address and telephone number of person
                authorized to receive notices and communications)

                                 March 16, 2010
             ------------------------------------------------------
            (Date of event which requires filing of this statement))

     If the filing person has previously filed a statement on Schedule 13G to
report the acquisition which is the subject of this Schedule 13D, and is filing
this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the
following box [ ].

     NOTE: Schedules filed in paper format shall include a signed original and
five copies of the schedule, including all exhibits. See Rule 13d-7 for other
parties to whom copies are to be sent.

                         (Continued on following pages)

                               (Page 1 of 7 Pages)

-------------------------------------------------------------------------------
     (1)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. 36229U102                 13D/A                   Page 2 of 7


-------------------------------------------------------------------------------
     (1)    NAME OF REPORTING PERSONS

                    Highbridge Capital Management, LLC

-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                   (a)  [ ]
                                                                   (b)  [X]

-------------------------------------------------------------------------------
     (3)    SEC USE ONLY

-------------------------------------------------------------------------------
     (4)    SOURCE OF FUNDS
                            OO

-------------------------------------------------------------------------------
     (5)    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS
            REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)                      [ ]

-------------------------------------------------------------------------------
     (6)    CITIZENSHIP OR PLACE OF ORGANIZATION
                   Delaware

-------------------------------------------------------------------------------
NUMBER OF      (7)  SOLE VOTING POWER
                    -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (8)  SHARED VOTING POWER
                    1,325,136 shares of Common Stock
OWNED BY       ----------------------------------------------------------------

EACH           (9)  SOLE DISPOSITIVE POWER
                    -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (10) SHARED DISPOSITIVE POWER
                    1,325,136 shares of Common Stock

-------------------------------------------------------------------------------
     (11)   AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
            1,325,136 shares of Common Stock

-------------------------------------------------------------------------------
     (12)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (11) EXCLUDES CERTAIN SHARES **                       [ ]

-------------------------------------------------------------------------------
     (13)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (11)
                    2.8% (See Item 4)

-------------------------------------------------------------------------------
     (14)   TYPE OF REPORTING PERSON
                    OO

-------------------------------------------------------------------------------





CUSIP No. 36229U102                 13D/A                   Page 3 of 7


-------------------------------------------------------------------------------

     (1)    NAME OF REPORTING PERSONS

            Highbridge International LLC

-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                   (a)  [ ]
                                                                   (b)  [X]

-------------------------------------------------------------------------------
     (3)    SEC USE ONLY

-------------------------------------------------------------------------------
     (4)    SOURCE OF FUNDS
                             WC

-------------------------------------------------------------------------------
     (5)    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS
            REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)                      [ ]

-------------------------------------------------------------------------------
     (6)    CITIZENSHIP OR PLACE OF ORGANIZATION
                   Cayman Islands, British West Indies

-------------------------------------------------------------------------------
NUMBER OF      (7)  SOLE VOTING POWER
                    -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (8)  SHARED VOTING POWER
                    1,325,136 shares of Common Stock
OWNED BY       ----------------------------------------------------------------

EACH           (9)  SOLE DISPOSITIVE POWER
                    -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (10) SHARED DISPOSITIVE POWER
                    1,325,136 shares of Common Stock

-------------------------------------------------------------------------------
     (11)   AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
            1,325,136 shares of Common Stock

-------------------------------------------------------------------------------
     (12)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (11) EXCLUDES CERTAIN SHARES                         [ ]

-------------------------------------------------------------------------------
     (13)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (11)
                   2.8% (See Item 4)

-------------------------------------------------------------------------------
     (14)   TYPE OF REPORTING PERSON
                   OO

-------------------------------------------------------------------------------





CUSIP No. 36229U102                 13D/A                   Page 4 of 7


-------------------------------------------------------------------------------
     (1)    NAME OF REPORTING PERSONS

                    Glenn Dubin

-------------------------------------------------------------------------------
     (2)    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                  (a)  [ ]
                                                                  (b)  [X]

-------------------------------------------------------------------------------
     (3)    SEC USE ONLY

-------------------------------------------------------------------------------
     (4)    SOURCE OF FUNDS
                              OO

-------------------------------------------------------------------------------
     (5)    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS
            REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)                    [ ]

-------------------------------------------------------------------------------
     (6)    CITIZENSHIP OR PLACE OF ORGANIZATION
                    United States

-------------------------------------------------------------------------------
NUMBER OF      (7)  SOLE VOTING POWER
                    -0-
SHARES         ----------------------------------------------------------------

BENEFICIALLY   (8)  SHARED VOTING POWER
                    1,325,136 shares of Common Stock
OWNED BY       ----------------------------------------------------------------

EACH           (9)  SOLE DISPOSITIVE POWER
                    -0-
REPORTING      ----------------------------------------------------------------

PERSON WITH    (10) SHARED DISPOSITIVE POWER
                    1,325,136 shares of Common Stock

-------------------------------------------------------------------------------
     (11)   AGGREGATE AMOUNT BENEFICIALLY OWNED
            BY EACH REPORTING PERSON
            1,325,136 shares of Common Stock

-------------------------------------------------------------------------------
     (12)   CHECK BOX IF THE AGGREGATE AMOUNT
            IN ROW (11) EXCLUDES CERTAIN SHARES                         [ ]

-------------------------------------------------------------------------------
     (13)   PERCENT OF CLASS REPRESENTED
            BY AMOUNT IN ROW (11)
                     2.8% (See Item 4)

-------------------------------------------------------------------------------
     (14)   TYPE OF REPORTING PERSON
            IN

-------------------------------------------------------------------------------





CUSIP No. 36229U102                 13D/A                   Page 5 of 7


Item 1.     Security and Issuer.

     This Amendment No. 4 (the "Amendment") amends the statement on Schedule 13D
filed on July 2, 2009 (the  "Original  Schedule  13D", as amended  hereby and by
Amendment  No. 1 filed on November 20, 2009,  Amendment  No. 2 filed on March 3,
2010 and  Amendment  No. 3 filed on March 16,  2010,  the  "Schedule  13D") with
respect to the common  stock,  no par value (the "Common  Stock"),  of GSI Group
Inc., a company  continued  and  existing  under the laws of the Province of New
Brunswick,  Canada  (the  "Issuer").  Capitalized  terms  used  herein  and  not
otherwise  defined in this Amendment have the meanings set forth in the Schedule
13D. This Amendment amends Items 4, 6 and 7 as set forth below.


Item 4.     Purpose of the Transaction.

Item 4 of the Schedule 13D is hereby amended and supplemented by the addition of
the following:

     On March 16, 2010  Highbridge  International  LLC and the other  Consenting
Noteholders entered into an Amended and Restated  Noteholder  Restructuring Plan
Support  Agreement (the "Amended and Restated Plan Support  Agreement") with the
Issuer  Parties,  amending and restating the Plan Support  Agreement.  Under the
Amended and  Restated  Plan  Support  Agreement  the parties  thereto  agreed to
modifications  to the Plan (the  "Modified  Plan") and to support  the  Modified
Plan.  The  Amended  and  Restated  Plan  Support  Agreement  contains  specific
agreements by the Consenting  Noteholders with respect to voting their claims in
support of the Modified  Plan as well as conditions  to the  termination  of the
Amended and Restated Plan Support Agreement which are  substantially  similar to
those contained in the Plan Support Agreement.

     As more fully  described in the Modified Plan,  under the Modified Plan the
Notes will be exchanged  for,  among other things,  New Senior Secured Notes (as
defined  in the  Modified  Plan) and New  Preferred  Shares  (as  defined in the
Modified Plan) which New Preferred  Shares will be convertible into common stock
of the  reorganized  Issuer.  The holders of the New Preferred  Shares will vote
together  with the holders of common  stock of the  reorganized  Issuer on an as
converted  basis. The terms of the New Preferred Shares are set forth as Exhibit
C to the Modified Plan. This  description of the Modified Plan is a summary only
and is qualified  in its  entirety by reference to the Modified  Plan, a copy of
which was filed as Exhibit A of Exhibit  10.1 of the Current  Report on Form 8-K
filed by the Issuer on March 19, 2010.

     This  description  of the Amended and Restated Plan Support  Agreement is a
summary  only and is  qualified  in its entirety by reference to the Amended and
Restated  Plan Support  Agreement,  a copy of which is  referenced  as Exhibit 8
hereto (which  incorporates  by reference  Exhibit 10.1 of the Current Report on
Form 8-K filed by the Issuer on March 19,  2010) and is  incorporated  herein by
reference.





CUSIP No. 36229U102                 13D/A                   Page 6 of 7


Item 6.       Contracts,  Arrangements,  Understandings  or  Relationships  with
Respect to Securities of the Issuer

Item 6 of the Schedule 13D is hereby amended and supplemented by the addition of
the following:

     As  described  in  Item 4  above,  on   March  16,  2010,   the  Consenting
Noteholders  entered into the Amended and Restated Plan Support  Agreement  with
the Issuer  Parties,  under which the parties  thereto  agreed to the terms of a
restructuring  of the Notes  pursuant to the  Modified  Plan, a copy of which is
referenced as Exhibit 8 hereto (which  incorporates by reference Exhibit 10.1 of
the  Current  Report on Form 8-K filed by the  Issuer on March 19,  2010) and is
incorporated herein by reference.

Item 7.       Material to Be Filed as Exhibits

Item 7 of the Schedule 13D is hereby amended and supplemented by the addition of
the following:

8. Amended and  Restated Noteholder Restructuring Plan Support  Agreement, dated
as of March 16, 2010,  by  and  among  the Consenting Noteholders and the Issuer
Parties (incorporated by reference to Exhibit 10.1 of the Current Report on Form
8-K filed by the Issuer on March 19, 2010).





CUSIP No. 36229U102                 13D/A                   Page 7 of 7


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:  March 19, 2010

HIGHBRIDGE INTERNATIONAL LLC               HIGHBRIDGE CAPITAL MANAGEMENT, LLC


By: Highbridge Capital Management, LLC     By: /s/ John Oliva
    its Trading Manager                        -------------------------------
                                           Name:  John Oliva
                                           Title: Managing Director

By: /s/ John Oliva
----------------------------------
Name:  John Oliva
Title: Managing Director




/s/ Glenn Dubin
----------------------------------
GLENN DUBIN