Exhibit 99.1
                          GSI GROUP REAFFIRMS GUIDANCE

Billerica, MA (October 28, 2005): GSI Group Inc., (Nasdaq: GSIG and TSX: GSI)
notes the recent sharp increase in trading volume over the past several days.
The Company confirms that there is no change in the Company's business
fundamentals and recent guidance.

GSI Group Inc. supplies precision motion control components, lasers and
laser-based advanced manufacturing systems to the global medical, semiconductor,
electronics, and industrial markets. GSI Group Inc's common shares are listed on
Nasdaq (GSIG) and The Toronto Stock Exchange (GSI). The Company's web site
address is www.gsig.com.

Certain statements in this news release may constitute forward-looking
statements within the meaning of the United States Private Securities Litigation
Reform Act of 1995 (the Reform Act), Section 27A of the United States Securities
Act of 1933 and Section 21E of the United States Securities and Exchange Act of
1934. These forward-looking statements may relate to anticipated financial
performance, management's plans and objectives for future operations, business
prospects, outcome of regulatory proceedings, market conditions, tax issues and
other matters. All statements contained in this news release that do not relate
to matters of historical fact should be considered forward-looking statements,
and are generally identified by words such as "anticipate," "believe,"
"estimate," "expect," "intend," "plan" and "objective" and other similar
expressions. Readers should not place undue reliance on the forward-looking
statements contained in this news release. Such statements are based on
management's beliefs and assumptions and on information currently available to
management and are subject to risks, uncertainties and changes in condition,
significance, value and effect. Other risks include the fact that the Company's
sales have been and are expected to continue to be dependent upon customer
capital equipment expenditures, which are, in turn, affected by business cycles
in the markets served by those customers. Other factors include volatility in
the semiconductor industry, the risk of order delays and cancellations, the risk
of delays by customers in introducing their new products and market acceptance
of products incorporating subsystems supplied by the Company, similar risks to
the Company of delays in its new products, our ability to continue to reduce
costs and capital expenditures, our ability to focus R&D investment and other
risks detailed in reports and documents filed by the Company with the United
States Securities and Exchange Commission and with securities regulatory
authorities in Canada. Such risks, uncertainties and changes in condition,
significance, value and effect, many of which are beyond the Company's control,
could cause the Company's actual results and other future events to differ
materially from those anticipated. The Company does not, however, assume any
obligation to update these forward-looking statements to reflect actual results,
changes in assumptions or changes in other factors affecting such
forward-looking statements.

GSI-G

For more information:
Raymond Ruddy
GSI Group Inc.
+1-978-439-5511
Ext. 6170