Exhibit  31.2
                  CERTIFICATION OF PRINCIPAL ACCOUNTING OFFICER


I,  Ann  Montgomery,  certify  that:

1.  I  have  reviewed this quarterly report on Form 10-Q of The GSI Group, Inc.;

2.  Based  on my knowledge, this report does not contain any untrue statement of
a  material  fact  or  omit  to  state  a  material  fact  necessary to make the
statements  made, in light of the circumstances under which such statements were
made,  not  misleading  with  respect  to  the  period  covered  by this report;

3.  Based  on  my  knowledge,  the  financial  statements,  and  other financial
information included in this report, fairly present in all material respects the
financial  condition,  results of operations and cash flows of the registrant as
of,  and  for,  the  periods  presented  in  this  report;

4.  The  registrant's  other  certifying  officer  and  I  are  responsible  for
establishing  and  maintaining disclosure controls and procedures (as defined in
Exchange  Act  Rules  13a-15(e)  and  15d-15(e))  for  the  registrant and have:

a)  designed  such disclosure controls and procedures, or caused such disclosure
controls  and  procedures  to  be designed under our supervision, to ensure that
material  information  relating  to  the  registrant, including its consolidated
subsidiaries,  is made known to us by others within those entities, particularly
during  the  period  in  which  this  report  is  being  prepared;

b)  evaluated  the  effectiveness  of  the  registrant's disclosure controls and
procedures  and presented in this report our conclusions about the effectiveness
of  the  disclosure controls and procedures, as of the end of the period covered
by  this  report  based  on  such  evaluation;  and

c) disclosed in this report any change in the registrant's internal control over
financial  reporting  that  occurred  during the registrant's most recent fiscal
quarter (the registrant's fourth fiscal quarter in the case of an annual report)
that  has materially affected, or is reasonably likely to materially affect, the
registrant's  internal  control  over  financial  reporting;  and

5.  The  registrant's  other  certifying officers and I have disclosed, based on
our  most recent evaluation of internal control over financial reporting, to the
registrant's auditors and the audit committee of registrant's board of directors
(or  persons  performing  the  equivalent  functions):

a)  all  significant  deficiencies  and  material  weaknesses  in  the design or
operation  of  internal  control  over  financial reporting which are reasonably
likely  to  adversely  affect  the  registrant's  ability  to  record,  process,
summarize  and  report  financial  information;  and

b)  any  fraud,  whether  or  not  material,  that  involves management or other
employees  who have a significant role in the registrant's internal control over
financial  reporting.

Date:  November  8,  2004

                                        /s/  Ann  Montgomery
                                        --------------------
                                         Vice  President  -  Finance  (Principal
                                          Accounting  Officer)