As filed with the Securities and Exchange Commission on October 10, 2008April 3, 2012

Registration No. 333-                333-180098

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON,Washington, D.C. 20549

Amendment No. 1

to

FORM S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

GSI GROUP INC.

(Exact Namename of Registrantregistrant as Specifiedspecified in its Charter)charter)

125 Middlesex Turnpike

Bedford, Massachusetts 01730

(781) 266-5700

(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

125 Middlesex Turnpike, Bedford, Massachusetts 01730

(Address of Principal Executive Offices)

Registrant’s telephone number, including area code: (781) 266-5700

Dr. Sergio Edelstein

President andJohn A. Roush, Chief Executive Officer

GSI Group Inc.

125 Middlesex Turnpike

Bedford, Massachusetts 01730

Telephone: (781) 266-5700

(Name, Address, includingIncluding Zip Code, and Telephone Number, includingIncluding Area Code, of Agent forFor Service)

Copies of all correspondenceCopy to:

Katharine A. Martin,James C. Gorton, Esq.

Robert Sanchez,Senet S. Bischoff, Esq.

Wilson Sonsini Goodrich & RosatiDennis G. Craythorn, Esq.

Professional CorporationLatham & Watkins LLP

650 Page Mill Road885 Third Avenue

Palo Alto, CA 94304New York, New York 10022

(650) 493-9300(212) 906-1200

Approximate Datedate of Commencementcommencement of Proposed Saleproposed sale to the Publicpublic:: From time to time after the effective date of this registration statement.

If the only securities being registered on this formForm are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  ¨

If any of the securities being registered on this formForm are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.  x

If this formForm is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this formForm is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this formForm is a registration statement pursuant to General Instruction I.D. or a post effectivepost-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.  ¨

If this formForm is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of large“large accelerated filer,” “accelerated filer,”filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one.)one):

The Registrantregistrant hereby amends this Registration Statementregistration statement on such date or dates as may be necessary to delay its effective date until the Registrantregistrant shall file a further amendment whichthat specifically states that this Registration Statementregistration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act, of 1933as amended, or until the Registration Statementthis registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said

Section 8(a), may determine.

EXPLANATORY NOTE

This Amendment No. 1 to the Registration Statement on Form S-3 of GSI Group Inc. (the “Company”) is being filed solely for the purpose of filing a revised Exhibit 5.1 to the Registration Statement and to add language to the section entitled “WHERE YOU CAN FIND MORE INFORMATION” to incorporate by reference certain documents filed by the Company under the Securities Exchange Act of 1934 prior to the effectiveness of the Registration Statement as contemplated by Division of Corporation Finance Compliance and Disclosure Interpretations, Securities Act Forms, Question 123.05.

Except as described above, no changes have been made to the Registration Statement.

The information in this prospectus is not complete and may be changed. The selling stockholdersWe may not sell these securities until the Registration Statementregistration statement filed with the Securities and Exchange Commission becomesis effective. This prospectus is not an offer to sell these securities and we areit is not soliciting offersan offer to buy these securities in any statejurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED OCTOBER 10, 2008

PROSPECTUS

Subject to completion, dated April 3, 2012.

GSI GROUP INC.Group Inc.

5,882,520 $200,000,000

Debt Securities

Common Shares

We may offer, from time to time, to sell any combination of debt securities and common shares described in this prospectus in one or more offerings. The aggregate initial offering price of the securities that we offer under this prospectus will not exceed $200,000,000. This prospectus provides a general description of the securities we may offer. Each time we sell securities, we will provide specific terms of the securities offered in a supplement to this prospectus. The prospectus supplement may also add, update or change information contained in this prospectus. You should read this prospectus and the applicable prospectus supplement carefully before you invest in any securities. This prospectus may not be used by us to sell securities unless accompanied by a prospectus supplement.

We may offer securities through underwriting syndicates managed or co-managed by one or more underwriters or dealers, through agents or directly to purchasers. The prospectus supplement for each offering of securities will describe in detail the plan of distribution for that offering. For general information about the distribution of securities, please see “Plan of Distribution” in this prospectus.

In addition, the selling stockholdersshareholder named in this prospectus on page 19 below are offeringmay offer, from time to selltime, up to an aggregate2,800,000 of 5,882,520 common shares, no par value, of GSI Group Inc. We issued these common shares to the selling stockholders upon the automatic exercise of warrants to purchase our common shares for $0.01 per share, which may be on a cashless basis, concurrently with the effective time of the registration statement of which this prospectus is a part. On August 20, 2008, we issued these warrants to the selling stockholders in a private placement and agreed to register the common shares issuable upon exercise of these warrants for resale under the Securities Act of 1933, as amended, pursuant to the registration statement of which this prospectus is a part.shares. We will not receive any of the proceeds from the sale of theour common shares that may be sold by the selling stockholders.shareholder. To the extent that any selling shareholder resells any common shares, the selling shareholder may be required to provide you with this prospectus and a prospectus supplement containing specific information about the offering.

The selling stockholdersshareholder may sell alloffer securities through underwriting syndicates managed or co-managed by one or more underwriters or dealers, through agents or directly to purchasers. For a portiondescription of the plan of distribution of the common shares beneficially owned by them and offered hereby from time to time directly or through one or more underwriters, broker-dealers or agents. If the common shares are sold through underwriters or broker-dealers, the selling stockholders will be responsible for underwriting discounts or commissions or agent’s commissions. The common shares may be sold in one or more transactions at fixed prices, at prevailing market prices at the time of the sale, at varying prices determined at the time of sale, or at negotiated prices. We provide more information about how the selling stockholders may sell their common shares in the section entitledshareholder, please see “Plan of Distribution” beginning on page 22 ofin this prospectus. We have agreed to pay all expensesIf required, the prospectus supplement for each offering of securities by the selling shareholder will describe in connection withdetail the registrationplan of these common shares.distribution for that offering.

Our common shares are tradedlisted for trading on the NASDAQ Global Select Market under the symbol “GSIG.” On October 9, 2008,March 13, 2012, the NASDAQ official closing price of our common shares on the NASDAQ Global Select Market was $2.41$11.51 per share.

Investing in our common sharessecurities involves a high degree of risk.risks. See “Risk Factors” beginning“Risk Factors” on page 42 of this prospectus, to read about factors you should consider before buying our common shares.in the documents incorporated into this prospectus and in any applicable prospectus supplement.

Neither the Securities and Exchange Commission, also referred to herein as the “SEC” or “Commission”, nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

The date of this prospectus is                  October [—], 2008.2012.

TABLE OF CONTENTS

i

ABOUT THIS PROSPECTUS

This prospectus is a part of a registration statement that we filed with the Securities and Exchange Commission, or the SEC, utilizing a “shelf” registration process. Under this shelf registration process, we may offer to sell any combination of the securities described in this prospectus in one or more offerings up to a total aggregate dollar amount of $200,000,000. This prospectus provides you with a general description of the securities we may offer. Each time we sell securities under this shelf registration, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. To the extent that any statement that we make in a prospectus supplement is inconsistent with statements made in this prospectus, the statements made in this prospectus will be deemed modified or superseded by those made in the prospectus supplement. We may only use this prospectus to sell the securities if it is accompanied by a prospectus supplement.

This prospectus also may be used by the selling shareholder identified in this prospectus to sell up to 2,800,000 of our common shares. We will not receive any proceeds from the sale of any of our common shares offered under this prospectus by the selling shareholder. To the extent that any selling shareholder resells any common shares, the selling shareholder may be required to provide you with this prospectus and a prospectus supplement containing specific information about the offering.

You should rely only on the information contained or incorporated by reference inread both this prospectus and any accompanying prospectus supplement. supplement, including all documents incorporated herein or therein by reference, together with additional information described under “Where You Can Find More Information.”

We have not, and the selling stockholders have not authorized any dealer, salesperson or other person to provide you withgive any information different from thator to make any representation other than those contained or incorporated by reference in this prospectus. The selling stockholders are offering to sell, and seeking offers to buy, our common shares only in jurisdictions where it is lawful to do so. The information in this prospectus is accurate only as of the date of this prospectus, regardless of the time of delivery of this prospectus or any saleaccompanying prospectus supplement. You must not rely upon any information or representation not contained or incorporated by reference in this prospectus or any accompanying prospectus supplement. This prospectus and any accompanying prospectus supplement do not constitute an offer to sell or the solicitation of our common shares.an offer to buy any securities other than the registered securities to which they relate, nor do this prospectus and any accompanying prospectus supplement constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction. You should not assume that the information contained in this prospectus and any accompanying prospectus supplement is accurate on any date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus and any accompanying prospectus supplement is delivered or securities are sold on a later date. Our business, financial condition, results of operations and prospects may have changed since that date.those dates.

ii

PROSPECTUS SUMMARYWHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC. The SEC maintains a web site,This summary highlightshttp://www.sec.gov, which contains reports, proxy and information statements and other information regarding registrants, including us, that file electronically with the SEC. You may read and copy any document we file with the SEC at its Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the Public Reference Room. You may also obtain these materials from us at no cost by directing a written or oral request to us at GSI Group Inc., 125 Middlesex Turnpike, Bedford, Massachusetts 01730, Attn: Investor Relations, or by calling our Investor Relations Department at (781) 266-5137, or at our website atwww.gsig.com. The information contained elsewhereon or accessible through our website is not incorporated by reference into this prospectus. Because it is a summary, it does not contain all ofprospectus or any prospectus supplement.

The SEC allows us to “incorporate by reference” certain information we file with the SEC, which means that we can disclose important information thatto you should consider before investing in our common shares. You should read this entire prospectus carefully, includingby referring to the section entitled “Risk Factors” andother information we have filed with the documentsSEC. The information that we incorporate by reference intois considered a part of this prospectus before making an investment decision. As usedand information that we file later with the SEC will automatically update and supersede the information contained in this prospectus. We incorporate by reference the following documents we filed with the SEC pursuant to Section 13 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”):

Notwithstanding the foregoing, unless specifically stated to the contrary, none of the information that we disclose under Items 2.02, 7.01 or 9.01 of any Current Report on Form 8-K that we may from time to time furnish to the SEC will be incorporated by reference into, or otherwise included in, this prospectus unless otherwise specified or any prospectus supplement.

We are also incorporating by reference additional documents that we may file with the context requires otherwise,SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of the initial registration statement and prior to effectiveness of the registration statement and after the date of this prospectus and the termination of this offering. These documents include periodic reports, such as Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, as well as Proxy Statements.

iii

DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the documents incorporated by reference in this prospectus or any prospectus supplement contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Such forward-looking statements are subject to certain risks and uncertainties, and typically can be identified by the use of words such as “may,” “expect,” “intend,” “could,” “estimate,” “anticipate,” “forecast,” “plan,” “believe” and similar terms. Although we believe that our expectations are reasonable, we can give no assurance that these expectations will prove to have been correct, and actual results may vary materially. Factors that could cause actual results to differ materially from those contemplated above include, among others:

iv

Additional factors which may cause actual results to differ materially from current expectations include, but are not limited to, those set forth in the section entitled “Business” in our Annual Report on Form 10-K for the year ended December 31, 2011, the section entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and the section titled “Risk Factors” in each of this prospectus, any prospectus supplement and in our Annual Report on Form 10-K for the year ended December 31, 2011. Please consider our forward-looking statements in light of those risks as you read this prospectus and any prospectus supplement.

v

ABOUT GSI GROUP INC.

GSI Group Inc. and its subsidiaries. Referencessubsidiaries (collectively referred to “selling stockholders” refer toas the holders listed herein under “Selling Stockholders” beginning on page 19, who may“Company”, “we”, “us”, or “ours” unless the context requires otherwise) design, develop, manufacture and sell shares from time to time as described in this prospectus.

GSI GROUP INC.

Overview

GSI Group Inc. designs, develops, manufactureslaser-based solutions (consisting of lasers and sells lasers,laser-based systems), laser systems, electro-opticalscanning devices, and precision motion and optical control components, air bearings, printers, color calibration devices and specialty optics.technologies. Our customers incorporate our technology is incorporated into theircustomer products or manufacturing processes for a wide range of applications in thea variety of markets, including: electronics, industrial, electronics, semiconductor, biomedical, medical, and aerospace markets.scientific. Our products allowenable customers to make advances in materials and processing technology and to meet extremely precise manufacturing specifications, including device complexityspecifications.

Our strategy is to drive sustainable, profitable growth through short-term and miniaturization.long-term initiatives, including:

GSI Group Inc., was founded and initially incorporated in Massachusetts in 1968 as General Scanning, Inc., was incorporated in Massachusetts. (“General Scanning”). General Scanning developed, manufactured and sold components and subsystems used for high-speed micro positioning of laser beams. In 1999, General Scanning merged its business with Lumonics Inc., a Canadian company that developed, manufactured and sold lasers and laser-based, advanced manufacturing systems for electronics, semiconductor, and general industrial applications. The post-merger entity, GSI Lumonics Inc., the post-merger entity, incorporatedcontinued under the laws of the Province of New Brunswick, Canada. In 2005, the Company renamed itselfwe changed our name to GSI Group Inc. GSI has manufacturing operations in North America, the United Kingdom and China, and sales and service offices in various locations around the world. GSI also has contractual relationships with various domestic and foreign distributors and resellers. As set forth more fully below, inIn August 2008, GSIwe acquired Excel Technology, Inc., a designer, manufacturer and marketer of photonics-based solutions consisting of lasers, laser-based systems, and precision motion devices.

Recent Transactions

Excel Technology, Inc. (“Excel”) develops, manufacturesdevices and sells lasers, laser-based systemselectro-optical components primarily used in industrial and precision motion devices. Excel manufactures its products in plants located in the United States and sells its products to customers worldwide, both directly and indirectly through resellers and distributors. On June 30, 2008, the Company formed Eagle Acquisition Corporation (“EAC”), a Delaware corporation and an indirect wholly owned subsidiary. On July 9, 2008, the Company and EAC entered into a merger agreement with Excel. On July 23, 2008, the Company commenced a tender offer to have EAC acquire all of Excel’s outstanding common stock for $32 per share, and thereafter to merge with and into Excel, with Excel surviving the merger and becoming an indirect wholly owned subsidiary of the Company. On August 29, 2008, the Company completed the Excel acquisition for approximately $360 million, exclusive of transaction costs.

On July 9, 2008, the Company and GSI Group Corporation, a wholly owned subsidiary, entered into a securities purchase agreement with the selling stockholders pursuant to which: (1) the Company issued and sold warrants to purchase up to an aggregate of 5,882,520 of GSI common shares at an exercise price of $0.01 per share,

payable in cash or by withholding of a certain number of common shares; and (2) GSI Group Corporation issued and sold $210,000,000 aggregate principal amount of 11.0% Senior Notes due 2013. The financing transaction closed on August 20, 2008, and the net proceeds were used to partially fund the Excel cash tender offer. The warrants were issued to the selling stockholders pursuant to a warrant agreement dated August 20, 2008. The Company intends to issue the common shares to the selling stockholders upon the automatic exercise of their warrants, which is expected to happen concurrently with the effective time of the registration statement of which this prospectus forms a part.

On August 20, 2008, the Company also entered into a registration rights agreement with the selling stockholders. The registration rights agreement requires the Company to file a registration statement of which this prospectus is a part and to use reasonable best efforts to cause the registration statement to become or be declared effective by October 28, 2008, or, if the SEC elects to review this registration statement, by November 12, 2008.

The merger agreement, the securities purchase agreement, the notes, the warrants, the warrant agreement and the registration rights agreement are more fully described in the Company’s Current Reports on Form 8-K filed with the SEC on July 11, 2008 and August 21, 2008. The foregoing description of the merger agreement, the securities purchase agreement, the notes, the warrants, the warrant agreement and the registration rights agreement is qualified in its entirety by reference to the actual agreements, each of which was included as an exhibit to the Company’s Current Report on Form 8-K filed with the SEC on July 11, 2008 and/or August 21, 2008, as applicable.

Company Informationscientific applications.

Our principal executive offices are located at 125 Middlesex Turnpike, Bedford, Massachusetts 01730, and our main telephone number is (781) 266-5700. Our website address ishttp://www.gsig.com. We do not incorporate by reference into this prospectus theThe information on, or accessible through, our website and you shouldis not consider it as part of this prospectus.

THE OFFERING

RISK FACTORS

Investing in our common sharessecurities involves risks. Prior to making a high degree of risk. Youdecision about investing in our securities, you should carefully consider carefully the risk factors described below, and all other information contained in or incorporated by reference in this prospectus before deciding to investor in any accompanying prospectus supplement, including, without limitation, the risks described in our common shares. IfAnnual Report on Form 10-K for the year ended December 31, 2011, which is incorporated herein by reference, the risk factors described under the caption “Risk Factors” in any applicable prospectus supplement and any risk factors set forth in our other filings with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the following risks actually occur,Exchange Act. Each of these risk factors could have a material adverse effect on our business, results of operations, financial position or cash flows, which may result in the market priceloss of our common shares could decline, and you could lose all or a part of your investment. AdditionalPlease read “Where You Can Find More Information” and “Disclosure Regarding Forward-Looking Statements” included elsewhere in this prospectus. Please note that additional risks not presently known to us, or that we currently believe aredeem immaterial, may also significantly impair our business operations and could result in a complete loss of your investment.

Risks Related to GSI Group

Merger with Excel

Our failure to successfully integrate Excel into our business may cause us to fail to realize the expected synergies and other benefits of the acquisition, which could adversely affect our future results.

The integration of Excel into our business presents significant challenges and risks to our businesses, including:

We may fail to successfully complete the integration of Excel into our business and, as a result, may fail to realize the synergies, cost savings and other benefits expected from the acquisition. We may fail to grow and build revenues and profits in Excel’s business lines or achieve sufficient cost savings through the integration of customers or administrative and other operational activities. Furthermore, we must achieve these objectives without adversely affecting our revenues. If we are not able to successfully achieve these objectives, the anticipated benefits of the acquisition may not be realized fully or at all, or it may take longer to realize them than expected, and our results of operations could be materially adversely affected.

Excel’s performance may not be in accordance with our expectations.

Despite our due diligence efforts, our assessment of the prospects for Excel’s business are subject to the risk associated with those businesses as described in Excel’s filings with the SEC, many of which are similar to the risks we face in our businesses and which are described below. Also, our ability to maintain and increase profitability of Excel’s business lines will depend on our ability to manage and control operating expenses and to generate and sustain increased levels of revenue. Our expectations to achieve more consistent and predictable levels of revenue and to increase Excel’s profitability may not be realized, and such revenues and profitability may decline as we integrate Excel’s operations into our business. If Excel’s revenues grow more slowly than we anticipate, or if its operating expenses are higher than we expect, we may not be able to sustain or increase its profitability, in which case our financial condition will suffer and our stock price could decline.operations.

Our substantial indebtedness could adversely affect our business and limit our ability to plan for or respond to changes in our business orUSE OF PROCEEDS

Unless we indicate otherwise in the competitive landscape.applicable prospectus supplement, we intend to use the net proceeds of the securities offered by us pursuant to this prospectus to acquire or invest in complementary businesses, technologies, products or intellectual property. We may also use the net proceeds of the securities offered by us pursuant to this prospectus for general corporate purposes, which may include the repayment or refinancing of outstanding indebtedness, capital expenditures and working capital. When a particular series of securities is offered, a prospectus supplement related to that offering will set forth our intended use of the net proceeds received from the sale of those securities.

As of September 26, 2008, the Company had consolidated indebtedness of approximately $210 million,The selling shareholder will receive all of which represents the debt incurred by GSI Group Corporation in connection withnet proceeds from the Excel transaction. The Company’s consolidated debt could have important and potentially materially adverse consequences on the Company’s business, including the following:

Market Volatility

Our business depends significantly upon capital expenditures which are subject to cyclical market fluctuations.

The semiconductor and electronics materials processing industries are cyclical and have historically experienced periods of oversupply, resulting in downturns in demand for capital equipment, including the products that we manufacture. The timing, length and severity of these cycles, and their impact on our business, are difficult to predict. Further, our order levels or results of operations for a given period may not be indicative of order levels or results of operations for subsequent periods. We can not assure investors that demand for our products will increase or that demand will not decrease. For the foreseeable future, our operations will continue to depend upon industries that are subject to market cycles, which, in turn, could adversely affect the market for the Company’s products.

Cyclical variations may have the most pronounced effect on our semiconductor systems segment, which has a concentration in the semiconductor and electronics industries.

There is no assurance that we will not be impacted from a slowdown as we have experienced in previous cyclical fluctuations or that the impact will be more or less significant compared to historical fluctuations.

Our business success depends upon our ability to respond to fluctuations in product demand.

If business declines, we may be required to reduce costs while at the same time maintaining the ability to motivate and retain key employees. We must also continually invest in research and development which may inhibit our ability to reduce costs in a down cycle. Additionally, long product lead-times create a risk that we may purchase or manufacture inventories of products that we are unable to sell. While we practice inventory management, we can offer no assurances that our efforts to mitigate this risk will be successful.

During a period of increasing demand and rapid growth, we must be able to increase manufacturing capacity quickly.

Our inability to quickly increase production in response to a surge in demand could harm our reputation and prompt customers to look for alternative sources of supply.

New Product Introduction

The success of our business requires that we continually innovate.

Technology requirements in our markets are consistently advancing. We must continually introduce new products that meet evolving customer needs. Our ability to grow depends on the successful development, introduction and market acceptance of new or enhanced products that address our customer’s requirements. Developing new technology is a complex and uncertain process requiring us to accurately anticipate technological and market trends and meet those trends with responsive products. Additionally, this requires that we manage the transition from older products to minimize disruption in customer ordering patterns, avoid excess inventory and ensure adequate supplies of new products. Failed market acceptance of new products or problems associated with new product transitions could harm our business.

Delays in delivery of new products could have a negative impact on our business.

Our research and development efforts may not lead to the successful introduction of products within the time period our customers demand. Additionally, our competitors may introduce new or improved products, processes or technologies that make our current or proposed products obsolete or less competitive.

In addition, we may encounter delays or problems in connection with our research and development efforts. Product development delays may result from numerous factors, including:

New products often take longer to develop, have fewer features than originally considered desirable and achieve higher cost targets than initially estimated. There may be delays in starting volume production of new products and/or new products may not be commercially successful.

Financial Matters

There may be a failure to properly identify when revenue should be recognized, leading to a material adverse effect on financial results.

The Company has multiple locations, in various countries, where orders are entered. Entry, shipment and invoicing of an order that is premature may result in revenue being recognized earlier than required by generally accepted accounting principles. To mitigate this risk, the Company reviews large systems orders for revenue recognition issues before they are booked. Additionally, the Company is putting in place more stringent processes to identify revenue recognition treatment on all orders.

Failure of internal controls or inability to identify or manage a key internal control could have a material adverse effect on our operating results.

We mitigate this risk by employing internal auditors to document and test our internal control procedures pursuant to Section 404 of the Sarbanes-Oxley Act. If we fail to achieve and maintain the adequacy of our internal controls, we may not be able to conclude that we have effective internal controls over financial reporting in accordance with Section 404. Effective internal controls, particularly those related to revenue recognition, are necessary for us to produce reliable financial reports and are important to prevent financial fraud. If we cannot provide reliable financial reports or prevent fraud, our business and operating results could be harmed, as investors could lose confidence in our reported financial information.

Our effective tax rates are subject to fluctuation, which could impact our financial position, and our estimates of tax liabilities may be subject to audit, which could result in additional tax assessments.

Our effective tax rates are subject to fluctuation as the income tax rates for each year are a function of taxable income levels in numerous tax jurisdictions, our ability to utilize recorded deferred tax assets, taxes or penalties resulting from tax audits and credits and deductions as a percentage of total taxable income. Further, tax law changes may cause our effective tax rates to fluctuate between periods.

Customer order timing and other factors beyond our control may lead to an inability to meet our financial forecasts.

Changes in customer order timing and the existence of certain other factors beyond our control may lead to our inability to meet financial forecasts. Such factors include:

A large percentage of our sales come from products with high selling prices and significant lead times. We may receive several large orders in one quarter from a customer and then receive no orders from that customer in the next quarter. As a result, the timing and recognition of sales from customer orders can cause significant fluctuations in our operating results from quarter to quarter.

A delay in a shipment or failure to meet our revenue recognition criteria near the end of a reporting period due, for example, to rescheduling or cancellations by customers or to unexpected difficulties experienced by us, may cause sales in the period to fall significantly below expectations and may have materially adverse effects on our operations for that period. Our inability to adjust quickly enough could magnify the adverse effects of that revenue shortfall on our results of operations.

As a result of these factors, our results of operations for any quarter are not necessarily indicative of results to be expected in future periods. We believe that fluctuations in quarterly results may cause the market pricessale of our common shares traded onoffered by it pursuant to this prospectus, and we will not receive any of the NASDAQ Global Select Stock Market to fluctuate, perhaps substantially.proceeds from the sale of such common shares.

GSIG maintains cash balances and foreign exchange contracts where significant changes in interest rates, credit ratings or foreign currency rates could result in materially adverse effects to income.RATIO OF EARNINGS TO FIXED CHARGES

The Companyfollowing table sets forth our ratios of earnings to fixed charges for the periods shown.

SELLING SHAREHOLDERS

The selling shareholder may sell a total of up to 2,800,000 common shares under this prospectus.

Under a registration rights agreement dated July 23, 2010, the selling shareholder has cash, cash equivalents and foreign exchange contracts that totala right to twice demand the registration of its registrable securities on a registration statement, subject to the limitations contained in the millions of dollars. These balances create financial exposure to changing interest and currency rates.registration rights agreement. The Company has attempted to mitigate these risks by both purchasing foreign exchange contracts and investing in government issued treasury bills. However, if long term interest rates or foreign currency rates were to change rapidly, the Company could incur material losses. Further, if management chooses to invest in less risk adverse investment vehicles, the risk of losing principle and/or interest could increase. Additionally, Excel owns certain auction rate securities for which there is no current market. Until such time as the auction rate securities market reopens, there is no assurance that these investments can become liquid.

International Operations

Our operations in foreign countries subject us to risks not faced by companies operating exclusively in the United States.

During the year ended December 31, 2007, approximately 68% of our revenue was derived from operations outside North America. International operations are an expanding part of our business both fromregistration may be a sales focus and an operating base.

Because of the scope of our international operations, we are subject to risks, which could materially impact our results of operations, including:

We cannot predict whether the United States or any other country will impose new quotas, tariffs, taxes or other trade barriers upon the importation of our products or supplies or gauge the effect that new barriers would have on our financial position or results of operations.

There are inherent risks as we increase our focus on overseas operations.

GSI currently manufactures certain of its products in plants in the United Kingdom and China. Manufacturing in overseas locations creates risks to the Company, including that we may not be able to produce products to the quality standards or deliver products on time as our customers have come to expect. This possibility may come about due to an inability to find qualified personnel overseas. It is also possible that after an overseas transition, we may find that we have been producing products with latent defects that come to light only after a long period of operation. Transitioning a business to an overseas location has many additional risks such as developing solid financial, enterprise resource planning (ERP) and customer relationship management (CRM) systems.

Economic, political or trade problems with foreign countries could negatively impact our business.

We are increasingly outsourcing the manufacture of sub assemblies to suppliers based in China and elsewhere overseas. Economic, political or trade problems with foreign countries could substantially impact our ability to obtain critical parts needed in the timely manufacture of our products.

Customs rules are complex and vary within legal jurisdictions in which we operate. Failure to comply with local customs regulations could be found during a foreign government customs audit that may produce a substantial penalty.

Customs rules are complex and vary within legal jurisdictions in which we operate and there can be no assurance that there will be no control failure around customs enforcement despite the precautions we take. A failure with local customs regulations could be found during a foreign government customs audit and could result in a substantial penalty and a material impact on our financial results. We seek to mitigate this risk by maintaining export control systems and an internal customs staff chargedshelf registration, filed with the responsibility of strictly complying with all applicable import/export laws. Further, we maintain arms length transactions with our foreign subsidiaries and their customers.

Economic Conditions

A halt in economic growth or a slowdown will put pressure on our ability to meet anticipated revenue levels.

A large portion of our sales is dependent on the need for increased capacity or replacement of inefficient manufacturing processes, because of the capital-intensive nature of our customers’ businesses. These sales also tend to lag behind in an economic recovery longer than other businesses. If a down turn lasts longer than expected, if a recovery does not begin or if a general economic slowdown commences, we may not be able to meet anticipated revenue levels on a quarterly or annual basis.

Debt Service

If the Company is unable to retire debt early, it may affect strategic options.

In connection with the acquisition of Excel, GSI borrowed $210 million, the proceeds of which were used to partially fund the Excel transaction. The loan agreement pursuant to which such funds were borrowed requires GSI to make twice annual debt service payments, and to retire the debt fully after five years. While GSI hopes to retire the debt in advance of that date, it is possible that this will not happen, and that GSI will be required to continue making substantial debt service payments throughout the term of the loan, affecting the Company’s business and strategic options.

Sustainable Profitability

If the Company is not able to grow, the business will be at greater risk to operate independently.

As a publicly traded company, GSIG is competing for capital and investment against larger companies. As a company with a relatively low level of stock capitalization, GSIG is at a disadvantage. Its cost of capital is higher than larger companies and it has less of a base to spread the operating costs that all public companies face. Examples of these costs include Sarbanes-Oxley and audit costs. If GSIG can not grow its revenues and spread these costs across a larger revenue base, it will be at a competitive disadvantage and potentially subject to a takeover bid from a larger company. We can not assure investors such a situation would be in stockholders’ best interests.

GSIG has a history of operating losses. The Company may not be able to sustain or grow the current level of profitability.

Since the second half of 2003, we have generated profits from operations. However, we incurred operating lossesSEC on an annual basis from 1998 through 2003. No assurances can be given that we will sustainunderwritten or increasenon-underwritten basis. In addition, the level of profitability inselling shareholder has unlimited piggyback registration rights.

The table below sets forth information regarding the future based on extrinsic market forces, and the market pricebeneficial ownership of our common shares may decline as a result.

We could lose some orby the selling shareholder. The information regarding the selling shareholder’s beneficial ownership after the sales made pursuant to this prospectus assumes that all of the benefitcommon shares subject to sale pursuant to this prospectus will have been sold. The selling shareholder has provided the information set forth below relating to the number of our deferred tax assets if our future profitability comes into question.

In determining our provision for income taxes, our deferred tax assets and liabilities and any valuation allowance recorded against our net deferred tax assets require subjective judgment and analysis. We consistently evaluate our current deferred tax assets based on profitability in 2008 and beyond. Our abilitycommon shares such shareholder currently owns. The common shares subject to maintain our deferred tax assets depends upon our abilitysale by the selling shareholder pursuant to continue to generate future profits in the United States, Canada, Germany, Japan and United Kingdom tax jurisdictions. If actual results differ from our plans or we do not achieve the desired level of profitability in a given jurisdiction, wethis prospectus may be requiredoffered from time to increasetime, in whole or in part, by the valuation allowance on our tax assets by taking a charge to the Statement of Operations, which could have a material negative result on our financial results.

Business Partnerships

Our reliance upon third party distribution channels subjects us to credit, inventory, business concentrationselling shareholder (and its nominees and business failure risks beyond our control.

We sell products through resellers, distributors, original equipment manufacturers (“OEMs”) and system integrators. Excel sells certain of its lasers through a 50% owned Indian joint venture. Selling products through third parties can subject the Company to credit and business risks. Our sales also depend upon the ability of our OEM customers to develop and sell systems that incorporate our products. Adverse economic conditions, large inventory positions, limited marketing resources and other factors influencing these OEM customers could have a substantial impact upon our financial results. We can not assure investors that our OEM customers will not experience financialsuccessors), donees, transferees or other difficulties that could adversely affect their operations and, in turn, our financial condition or results of operations.successors-in-interest.

Intellectual PropertyDESCRIPTION OF COMMON SHARES

We are exposed to the risks that others may violate our intellectual property rights.

Our future success depends in part upon our intellectual property rights, including trade secrets, know-how and continuing technological innovation. There can be no assurance that the steps we take to protect our intellectual property rights will be adequate to prevent misappropriation, or that others will not develop competitive technologies or products outside of our patented property. There can be no assurance that other companies are not investigating or developing other technologies that are similar to ours, that any patents will issue from any application filed by us or that, if patents do issue, the claims allowed will be sufficiently broad to deter or prohibit others from marketing similar products. In addition, there can be no assurance that any patents issued to us will not be challenged, invalidated or circumvented in a legal or administrative proceeding, or that our patents and know how will provide a competitive advantage to us.

Our intellectual property rights may not be protected in foreign countries.

Our efforts to protect our intellectual property rights may not be effective in some foreign countries where we operate or sell. Many U.S. companies have encountered substantial problems in protecting their property rights against infringement in foreign countries. If we fail to adequately protect our intellectual property in these countries, it could be easier for our competitors to sell competing products in foreign countries.

Our success depends upon our ability to protect our intellectual property and to successfully defend against claims of infringement by third parties.General

We have receivedauthority to issue an unlimited number of common shares, no par value. As of February 29, 2012, 33,515,041 common shares were issued and outstanding. As of February 29, 2012, we had an aggregate of 712,641 common shares reserved for issuance upon vesting of restricted stock unit awards granted under our 2010 Incentive Award Plan, as amended, or our Amended 2010 Plan, 169,864 common shares reserved for issuance upon settlement of deferred stock units granted to our directors pursuant either to stand-alone award agreements that are independent from an equity plan or the Amended 2010 Plan, 6,536 common shares reserved for issuance upon the vesting of restricted stock awards granted under our prior equity plans that were cancelled upon our emergence from bankruptcy on July 23, 2010, and 1,944,168 common shares reserved for issuance pursuant to future grants under our Amended 2010 Plan.

Terms

Each outstanding common share is entitled to one vote at all meetings of our shareholders, to participate ratably in the past, and could receive in the future, notices from third parties alleging that our products infringe patent or other proprietary rights. We believe that our products are non-infringing or that we have the patents and/or licenses to allow us to lawfully sell our products throughout the world. However, weany dividends which may be sued for infringement. Indeclared by the event any third party makes a valid claim against us or our customers for which a license was not available to us on commercially reasonable terms, we would be adversely affected. Adverse consequences may also apply to our failure to avoid litigation for infringement or misappropriationboard of proprietary rights of third parties.

Competition

We operate in highly competitive industries,directors and, if we lose competitive advantages, our business would suffer adverse consequences.

Some of our competition comes from established competitors, some of which have greater financial, engineering, manufacturing and marketing resources than we do. Our competitors will continue to improve the design and performance of their products and introduce new products. It is possible that we may not successfully differentiate our current and proposed products from the products of our competitors, or that the marketplace will not consider our products to be superior to competing products. To remain competitive, we will be required to invest heavily in research and development, marketing and customer service and support. It is also possible that we may not be able to make the technological advances necessary to maintain our competitive position, or our products will not receive market acceptance. We may not be able to compete successfully in the future, and increased competition may result in price reductions, reduced profit margins, loss of market share and an inability to generate cash flows that are sufficient to maintain or expand our development of new products.

Mergers and Acquisitions

Our business strategy includes finding and making strategic acquisitions and divestitures. There can be no assurance that we will be able to continue to make acquisitions that provide business benefit.

In 2007, we acquired an optics business in the United Kingdom. We acquired Excel in August 2008 and sold a U.S. optics business in September 2008. We expect to continue to evaluate potential acquisitions and divestitures as part of our long-term strategic plan. Our identification of suitable acquisition candidates involves risks inherent in assessing the values, strengths, weaknesses, risks, synergy and profitability of acquisition candidates, including the effects of the possible acquisition on our business, diversion of management’s attention from our core businesses and risks associated with unanticipated problems or liabilities. We cannot assure investors our efforts will be sufficient, or that acquisition candidates will be receptive to our advances or that any acquisition we may make would be accretive to earnings. We also cannot assure investors that we will find suitable purchasers in the event that we identifyof liquidation, dissolution or winding-up or other distribution of our assets or property, to a potential divestiture candidate in the future.

Integrating an acquisition couldpro rata share of our assets after payment of all our liabilities and obligations. We have significant disruptive consequencesnever declared or paid cash dividends on our existing operations.

As withcommon shares. We currently intend to retain any acquisition, those persons selling have an advantage in better understanding the specific markets and their associated direction. They also better know the strengths and weaknesses of the business they are selling. We attempt to mitigate these risks by focusing our attention on the acquisition of businesses, technologies and products that have current relevancy to our existing lines of business and that are complementary to our existing product lines. However, we may not be successful in addressing these risks, or the risks associated with the potential entrance into markets in which we have limited or no prior experience. We could lose key employees, particularly those of the acquired business, in connection with an acquisition.

Key Personnel

GSIG is undergoing a leadership transition.

Subsequent to the Excel transaction, GSI has been reviewing its management structure, and has reviewed, and may continue to review, its business and organizational structure. There are risks associated with changes in strategy and management at the executive and/or director level, and changes in product or operational focus. There can be no assurance that prospective management changes will not have a material effect on the Company.

Our operations could be negatively affected if we lose key executives or employees or are unable to attract and retain skilled executives and employees as needed.

Our business and future operating results depend in part upon our abilityearnings to attract, groomfinance the growth and retain qualified management, technical, sales and support personnel for our operations on a worldwide basis. The lossdevelopment of key personnel could negatively impact our operations. Competition for qualified personnel is intense and we cannot guarantee that we will be able to continue to attract, train and retain qualified personnel.

Our reputation and our ability to do business may be impaired by improper conduct by any of our employees, agents or business partners.

We cannot provide assurance that our internal controls will always protect us from reckless or criminal acts committed by our employees, agents or business partners that would violate US and/or non-US laws, including the laws governing payments to government officials, competition, money laundering and data privacy. Any such improper actions could subject us to civil or criminal investigations in the US and in other jurisdictions, and could lead to substantial civil or criminal, monetary and non monetary penalties against us or our subsidiaries.

Operations

We expect to be consolidating some of our operations for greater efficiency.

There is execution risk in these plans. We can not assure investors that economies of scale will or can be realized as a result of any planned consolidation. This move will take time and will include substantial operational risks, including the possible disruption of manufacturing lines. We can not assure investors that any moves would not disrupt business operations or have a material impact on results.

In addition, any decision to limit investment in, dispose of or otherwise exit business activities may result in the recording of special charges, such as technology write-offs, workforce reduction costs, or charges relating to consolidation of excess facilities. Our estimates with respect to the useful life or ultimate recoverability of our carrying basis of assets, including intangible assets, could change as a result of such decisions. Further, our estimates related to the liabilities for excess facilities are affected by changes in real estate market conditions. Additionally, we are required to perform goodwill impairment tests on an annual basis and during the year in certain circumstances. There can be no assurance that future goodwill impairment tests will not result in a change to earnings.

We have recently undergone a significant restructuring and we will continue to change our management structure.

Our ability to reduce operating expenses is dependent upon the nature of the actions we take to reduce expense and subsequent ability to implement those actions and realize expected cost savings. In the past year, management took significant actions to expand our operations in China and to reduce expenses, particularly within GSI’s U.S.-based organization and in the United Kingdom. There can be no assurance that these actions will provide economic benefit to the Company. Further, there is a risk that these actions may ultimately prove detrimental to operations and sales, or to our intellectual property protections.

Product defects or problems with integrating our products with other vendors’ products may seriously harm our business and, reputation.therefore, do not anticipate paying any cash dividends in the foreseeable future.

Complex products that we produce can contain latent errorsShareholders have cumulative voting rights in the election of directors. Cumulative voting rights permit each shareholder entitled to vote at a meeting of shareholders called for the election of directors to cast a number of votes equal to the number of shares held by the shareholder multiplied by the number of directors to be elected. The shareholder is entitled to cast all such votes in favor of one candidate for director or performance problems.distribute them among the candidates in any manner.

The common shares are not liable to any calls or assessments and are not convertible into any other securities. There have been instances where we have found errors immediately after launch of new products,are no redemption or sinking fund provisions applicable to the common shares, and there have been instances where we have also found latent errors in our products. We cannot always resolve all errors that we believe would be considered seriousare no preemptive rights held by our customers before implementation, thus our products are not error-free. These errors or performance problems could be detrimental to our business and reputation. In addition, customers frequently integrate our products with other vendor’s products. When problems occur in a combined environment, it may be difficult to identify the sourceholders of the problem. These problems may cause uscommon shares.

All outstanding common shares are fully paid and non-assessable, and common shares offered pursuant to incur significant warrantythis prospectus will, when issued, be fully paid and repair costs, divert the attention of our engineering personnel from our product development efforts and cause significant customer relations problems. To date, defects in our products or those of other vendors’ products with which our products are used by our customers have not had a material negative effect on our business. However, we cannot be certain that a material negative impact will not occur in the future.non-assessable.

We depend on limited source suppliers that could cause substantial manufacturing delays if supply disruption occurs.

Many of our products are manufactured with components that are designed by an outside supplier to our specifications. While we attempt to mitigate risks associated with our reliance on single suppliers by actively managing our supply chain, we still source some components from single vendors. We also rely on a limited number of independent contractors to manufacture subassemblies for some of our products, particularly in our Semiconductor Systems. There can be no assurance that our current or alternative sources will be able to continue to meet all of our demands on a timely basis. If suppliers or subcontractors experience difficulties, or fail to meet any

of our manufacturing requirements, our business would be harmed until we are able to secure alternative sources, if any, on commercially reasonable terms.

We also depend on suppliers that provide high precision parts.

Any of these parts that have latent or known defects, may materially impact relations with our customers if they cause us to miss our scheduled shipment deadlines. If latent defects are incorporated into our products and discovered later, there could be a material impact on our revenues. We seek to reduce the risk of defects by selecting and qualifying alternative suppliers for key parts, and by monitoring the quality of products coming from key suppliers.

Production difficulties and product delivery delays could materially adversely affect our business.

We assemble our products at our facilities in the United States, the United Kingdom and China. If use of any of our manufacturing facilities was interrupted by a natural disaster or otherwise, our operations could be negatively impacted until we could establish alternative production and service operations. In addition, we may experience production difficulties and product delivery delays in the future as a result of:

Governance

Certain provisions of our articles of incorporation may delay or prevent a change in control of our company.Anti-Takeover Considerations

Our corporate documents and our existence as a corporation under the laws of New Brunswick subject us toArticles contain provisions of Canadian law that may enable our board of directors to resist a change in control of our company. These provisions include:

These anti-takeover defenses could discourage, delay or prevent a transaction involving a change in control of our company. These provisions could also discourage proxy contests and make it more difficult for stockholdersshareholders to elect directors of their choosing andor cause us to take other corporate actions that stockholdersshareholders desire.

Compliance with changing regulationCanadian Law Matters

There is no limitation imposed by Canadian law or by our Articles on the right of corporate governance and public disclosure maya non-resident to hold or vote common shares, other than as provided in the Investment Canada Act (the “ICA”). Unless a transaction falls

within an available exemption, the ICA requires a non-Canadian making an investment which would result in additional expenses.the acquisition of control of a Canadian business or an investment to establish a new Canadian business, to identify, notify, or (if the value of the assets of the target Canadian business exceed a certain monetary threshold, or if the transaction is considered to be an investment that could be injurious to Canadian national security) file an application for review with the Investment Review Division of Industry Canada (“IRD”).

The notification procedure involves a brief statement of information about the investment on a prescribed form which is required to be filed with the IRD by the investor at any time up to 30 days following implementation of the investment. It is intended that investments requiring only notification will proceed without government intervention unless the investment is in a specific type of business activity related to Canada’s cultural heritage and national identity.

If an investment is reviewable under the ICA, an application for review in the form prescribed is normally required to be filed with the IRD prior to the investment taking place and the investment may not be implemented until the review has been completed and the Minister of Industry (“Minister”) (the Minister responsible for Investment Canada) is satisfied that the investment is likely to be of net benefit to Canada (and, if applicable, is satisfied that the investment would not be injurious to Canadian national security). The Minister has up to 75 days to make this determination, though this period can be extended by agreement between the IRD and the investor (a national security review can take up to 130 days). If the Minister is not satisfied that the investment is likely to be of net benefit to Canada, the non-Canadian must not implement the investment or, if the investment has been implemented, may be required to divest himself of control of the business that is the subject of the investment. If the Governor in Council considers that it is advisable to protect national security, she may prohibit the investment, authorize it to proceed on conditions, or require divestiture.

Canada has no system of exchange controls. There are no Canadian restrictions on the repatriation of capital or earnings of a Canadian public company to non-resident investors. There are no laws in Canada or exchange restrictions affecting the remittance of dividends, profits, interest, royalties or other payments to non-resident holders of Common Shares, except as described under “Canadian Taxation Matters”.

Canadian Taxation Matters

Changing laws,The following summary is based upon the current provisions of theIncome Tax Act (Canada) (the “Tax Act”), the current provisions of the regulations promulgated thereunder (the “Regulations”) and standardsthe current provisions of the Canada-United States Tax Convention (the “Treaty”), as at the date hereof and counsel’s understanding of the current administrative practices of the Canada Revenue Agency (the “CRA”). This summary takes into account all specific proposals to amend the Tax Act and the Regulations that have been publicly announced by, or on behalf of, the Minister of Finance (Canada) prior to the date of this registration statement on Form S-3 (the “Tax Proposals”), but does not otherwise take into account or anticipate any changes in law, whether by judicial, governmental or legislative decision or action, or changes in administrative practices of the CRA. No assurances can be given that the Tax Proposals will be enacted as proposed, if at all. This summary does not take into account the tax legislation of any province or territory of Canada or any non-Canadian jurisdiction. Provisions of provincial income tax legislation vary from province to province in Canada and in some cases differ from federal income tax legislation.

The Tax Act contains certain provisions relating to corporate governancesecurities held by certain financial institutions (the “mark-to-market rules”). This summary does not take into account the mark-to-market rules and public disclosure,investors that are financial institutions for the purposes of those rules should consult their own tax advisors. This summary is not applicable to investors an interest in which would be a “tax shelter investment”, as defined in the Tax Act, and any such investor should consult their own tax advisors.

The following summary is of a general nature only and is not intended to be, nor should it be construed to be, legal or tax advice to any particular investor. This summary is not exhaustive of all

Canadian federal income tax considerations. Accordingly, investors should consult their own tax advisors with respect to their particular circumstances, including the Sarbanes-Oxleyapplication and effect of the income and other taxes of any country, province, territory, state or local tax authority.

The following summary is generally applicable to an investor who, at all relevant times, for purposes of the Tax Act of 2002, new regulations promulgated byand any applicable income tax treaty or convention, is neither resident nor deemed to be resident in Canada, is not affiliated with the SEC andCompany for the rulespurposes of the Tax Act, deals at arm’s length with the Company for the purposes of the Tax Act, holds common shares as capital property and does not use or hold, and is not deemed to use or hold common shares in connection with carrying on business in Canada (a “non-resident shareholder”). Special rules, which are not discussed in this summary, may apply to a non-resident shareholder that is an insurer that carries on an insurance business in Canada and elsewhere.

Dividends on Common Shares

Generally, dividends (including stock dividends) paid or credited (including amounts on account of or in lieu of dividends) by Canadian corporations to non-resident shareholders are subject to a withholding tax of 25 percent. However, the Treaty provides for a 15 percent withholding tax on dividends paid to all individuals and corporate residents of the United States that qualify for benefits under the Treaty. Dividends paid to any non-resident company that qualifies for benefits under the Treaty and that beneficially owns at least 10 percent of the voting stock of the payer company are subject to withholding tax at 5 percent.

Dividends (including stock dividends) paid or credited to a holder that is a United States tax-exempt organization, as described in Article XXI of the Treaty, and is entitled to the benefits of Article XXI(2) of the Treaty will not have to pay any Canadian withholding tax in respect of the amount of the dividend.

Disposition of Common Shares

A non-resident shareholder will not be subject to tax under the Tax Act on any capital gain realized on a disposition of a Common Share unless the common shares constitute “taxable Canadian property” to the non-resident shareholder. Generally, common shares will not constitute “taxable Canadian property” to a non-resident shareholder at a particular time provided that (a) the common shares are listed on a designated stock exchange at that time, (b) the non-resident shareholder, persons with whom the non-resident shareholder does not deal at arm’s length, or the non-resident shareholder together with persons with whom the non-resident shareholder does not deal at arm’s length, have not owned 25% or more of the issued shares of any of the classes (or of any series within a class) of the Company at any time during the 60-month period that ends at that time, and (c) less than 50% of the fair market value of the share is derived, directly or indirectly, from one or any combination of real or immovable property in Canada, Canadian resource properties, timber resource properties or options in respect of, or interests or rights in, such properties. Common shares may also be taxable Canadian property in certain other circumstances, including where the non-resident shareholder elected to have them treated as taxable Canadian property upon ceasing to be resident in Canada. Notwithstanding the foregoing, in certain circumstances set out in the Tax Act, common shares could be deemed taxable Canadian property. Non-resident shareholders should consult their own tax advisors to determine whether the common shares will constitute taxable Canadian property in their particular circumstances.

Even if the common shares are taxable Canadian property to a non-resident shareholder, a taxable capital gain or an allowable capital loss resulting from the disposition of the shares will not be included in computing the non-resident shareholder’s income for the purposes of the Tax Act if the common shares constitute “treaty-protected property”. Common shares owned by a non-resident shareholder will generally be treaty-protected property if the gain from the disposition of such property would, because of an applicable income tax treaty or convention to which Canada is a signatory, be exempt from tax under the Tax Act. Non-resident shareholders should consult their own tax advisors to determine whether the common shares constitute treaty-protected property in their particular circumstances.

Under the Tax Act, the disposition of a common share by a holder may occur in a number of circumstances including on a sale or gift of the common share or upon the death of the holder. There are no Canadian federal estate or gift taxes on the purchase or ownership of the common shares.

All non-resident shareholders who dispose of “taxable Canadian property” are required to file a Canadian tax return reporting their gain or loss on the disposition and, subject to an applicable tax treaty exemption, pay the Canadian federal tax due on the disposition.

All non-resident shareholders who dispose of “taxable Canadian property” are also required to obtain an advance clearance certificate in respect of their disposition under section 116 of the Tax Act (the “Section 116 Certificate”). The purchaser of the common shares is obligated to withhold 25% of the gross proceeds on the acquisition of the common shares from a non-resident shareholder except to the extent of the certificate limit on the Section 116 Certificate. A Section 116 Certificate is required even where the gain is exempt from Canadian income tax under a provision of an income tax treaty with Canada, such as the Treaty. If the non-resident shareholder does not provide a Section 116 Certificate to the purchaser, then the purchaser will be required to withhold and remit to the CRA 25% of the proceeds on account of the non-resident shareholder’s tax obligation, on or before the end of the month following the date of the sale. The non-resident shareholder may then file a Canadian tax return to obtain a refund of excess withholding tax, if any.

Transfer Agent

The registrar and transfer agent for our common shares is Computershare Investor Services.

Listing

Our common shares are listed on The NASDAQ Global Select Market are resulting in increased general and administrative expenses for companies such as ours. These new or changed laws, regulations and standards are subject to varying interpretations in many cases, and as a result, their application in practice may evolve over time as new guidance is provided by regulatory and governing bodies,under the symbol “GSIG.”

DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplement, summarizes certain general terms and provisions of the debt securities that we may offer under this prospectus. When we offer to sell a particular series of debt securities, we will describe the specific terms of the series in a supplement to this prospectus. We will also indicate in the prospectus supplement the extent to which could resultthe general terms and provisions described in higher costs necessitated by ongoing revisionsthis prospectus apply to disclosurea particular series of debt securities.

We may issue debt securities either separately, or together with, or upon the conversion or exercise of or in exchange for, other securities described in this prospectus. Debt securities may be our senior, senior subordinated or subordinated obligations and, governance practices. We are committedunless otherwise specified in a supplement to maintaining high standards of corporate governancethis prospectus, the debt securities will be our direct, unsecured obligations and public disclosure. As a result, we intend to invest resources to comply with evolving laws, regulations and standards, and this investment may resultbe issued in increased general and administrative expensesone or more series.

The debt securities will be issued under an indenture between us and a diversion of management time and attention from revenue-generating activitiestrustee to compliance activities. If our efforts to comply with new or changed laws, regulations and standards differ frombe identified in the activities intended by regulatory or governing bodies, our business may be harmed.

Regulation

Increased governmental regulation of our business could materially adversely affect our business.

applicable prospectus supplement. We are subject to many governmental regulations, including but not limited to the laser radiation safety regulationshave summarized select portions of the Radiation Control for Health and Safety Act administered by the National Center for Devices and Radiological Health, a branchindenture below. The summary is not complete. The form of the United States Food and Drug Administration, and certain health regulations relatedindenture has been filed as an exhibit to the manufacture of products using beryllium, an element used in some of our structures and mirrors. Among other things, these regulations require us to file annual reports, to maintain quality control and sales records, to perform product testing, to distribute appropriate operating manuals, to incorporate design and operating features in products sold to end-users and to certify and label our products. Various warning labels must be affixed and certain protective devices installed depending on the class of product. We are subject to regulatory oversight, including comparable enforcement remedies, in the markets we serve.

Changes in governmental regulations may reduce demand for our products or increase our expenses.

We compete in many markets in which we and our customers must comply with federal, state, local and international regulations, such as environmental, health and safety and food and drug regulations. We develop, configure and market our products to meet customer needs created by those regulations. Any significant change in regulations could reduce demand for our products, which in turn could materially adversely affect our business, operating results and financial condition.

Risks Relating to Ownership of Our Common Shares

Holders of our common shares are subject to the risk of additional and substantial dilution to their interests as a result of future issuances of common shares.

Upon the effectiveness of the registration statement of which this prospectus forms a part warrantsand you should read the indenture for provisions that may be important to purchase upyou. In the summary below, we have included references to an aggregatethe section numbers of 5,882,520the indenture so that you can easily locate these provisions. Capitalized terms used in the summary and not defined herein have the meanings specified in the indenture.

As used in this section only, “GSI Group,” “we,” “our” or “us” refer to GSI Group Inc. excluding our subsidiaries, unless expressly stated or the context otherwise requires.

General

The terms of each series of debt securities will be established by or pursuant to a resolution of our common shares for $0.01 per shareboard of directors and set forth or determined in the manner provided in a resolution of our board of directors, in an officer’s certificate or by a supplemental indenture. (Section 2.2) The particular terms of each series of debt securities will be automatically exerciseddescribed in a prospectus supplement relating to such series (including any pricing supplement or term sheet).

We can issue an unlimited amount of debt securities under the indenture that may be in one or more series with the same or various maturities, at par, at a premium, or at a discount. (Section 2.1) We will set forth in a prospectus supplement (including any pricing supplement or term sheet) relating to any series of debt securities being offered, the aggregate principal amount and 5,882,520the following terms of the Company’s common sharesdebt securities, if applicable:

our current reports on Form 8-K filed with the SEC on March 20, 2008, April 30, 2008, July 3, 2008, July 11, 2008, July 18, 2008, July 31, 2008, August 21, 2008, August 29, 2008, September 2, 2008, October 9, 2008 and October 10, 2008; and            , 2012

Any information in any of the foregoing documents will automatically be deemed to be modified or superseded to the extent that information in this prospectus or in a later filed document that is incorporated or deemed to be incorporated herein by reference modifies or replaces such information.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

The following table sets forth the estimated costs and expensesfees payable by GSI Group Inc. (the “Registrant”) in connection with the sale of the securities being registered hereby. The expenses of registration of the common shares being registered. Theoffered by the selling stockholdersshareholder will not bear any portionbe borne by us in accordance with the registration rights agreement. With the exception of such expenses. All the Securities and Exchange Commission registration fee, all amounts shown are estimates, except for the SEC registration fee.estimates.

TheOur by-laws of the Registrant require the Registrant tothat we indemnify current or former directors and officers against expenses incurred by them in connection with each proceeding in which such officer or director is involved as a result of serving or having served at the Registrant’sour request. The Registrant’sOur indemnification obligation covers all costs, charges and expenses, including amounts paid to settle an action or satisfy a judgment reasonably incurred by such officer or director by reason of having been an officer or director. Indemnification is not available with respect to a proceeding as to which it has been adjudicated that such person did not act honestly and in good faith with a view to theour best interests, of the Registrant, and, with the reasonable belief that his or her action was lawful. The above provisions are intended to follow and are subject to the limitations set forth in section 81 of the New Brunswick Business Corporations Act.Act (“NB BCA”).

Section 81(1) of the NB BCA provides that except in respect of an action by or on behalf of us or a body corporate to procure a judgment in its favor, we may indemnify a former or current director or officer or other person who acts or acted at our request as a director or officer of a body corporate of which we are or were a shareholder or creditor, and that person’s heirs and legal representatives, against all costs, charges and expenses, including an amount paid to settle an action or satisfy a judgment, reasonably incurred by that person in respect of any civil, criminal or administrative action or proceeding to which that person is made a party by reason of being or having been a director or officer of the Company or body corporate, if (a) that person acted honestly and in good faith with a view to our best interests, and (b) in the case of a criminal or administrative action or proceeding that is enforced by a monetary penalty, that person had reasonable grounds for believing that that person’s conduct was lawful.

Section 81(2) of the NB BCA provides that we may with court approval indemnify a former or current director or officer or other person who acts or acted at our request as a director or officer of a body corporate of which we are or were a shareholder or creditor, and that person’s heirs and legal representatives in respect of an action by or on behalf of us or body corporate to procure a judgment in its favor, to which he is made a party by reason of being or having been a director or an officer of the Company or body corporate, against all costs, charges and expenses reasonably incurred by him in connection with such action if (a) that person acted honestly and in good faith with a view to our best interests, and (b) in the case of a criminal or administrative action or proceeding that is enforced by a monetary penalty, that person had reasonable grounds for believing that that person’s conduct was lawful.

II-1

Section 81(3) of the NB BCA provides that notwithstanding anything in section 81 of the NB BCA, a former or current director or officer or other person who acts or acted at our request as a director or officer of a body corporate of which we are or were a shareholder or creditor, and that person’s heirs and legal representatives is entitled to indemnity from us in respect of all costs, charges and expenses reasonably incurred by him in connection with the defense of any civil, criminal or administrative action or proceeding to which he is made a party by reason of being or having been a director or officer of the Company or body corporate, if the person seeking indemnity (a) was substantially successful on the merits of his defense of the action or proceeding, (b) acted honestly and in good faith with a view to our best interests, (c) in the case of a criminal or administrative action or proceeding that is enforced by a monetary penalty, had reasonable grounds for believing that that person’s conduct was lawful and (d) is fairly and reasonably entitled to indemnity.

Section 81(4) of the NB BCA provides that we may purchase and maintain insurance for the benefit of any former or current director or officer or other person who acts or acted at our request as a director or officer of a body corporate of which we are or were a shareholder or creditor, and that person’s heirs and legal representatives against any liability incurred by him (a) in his capacity as our director or officer, except where the liability relates to his failure to act honestly and in good faith with a view to our best interests; or (b) in his capacity as a director or officer of another body corporate if he acts or acted in that capacity at our request, except where the liability relates to his failure to act honestly and in good faith with a view to the best interests of that body corporate.

We and our wholly owned subsidiary, GSI Group Corporation, have also entered into indemnification agreements with our chief executive officer and chief financial officer. The Registrantindemnification agreements provide that we will indemnify such persons if they are, or are threatened to be made, a party to or a participant in any proceeding, other than a proceeding by or in the right of us to procure a judgment in our favor. Such persons are indemnified to the fullest extent permitted by applicable law against all expenses, judgments, fines and amounts paid in settlement actually and reasonably incurred by them or on their behalf in connection with such proceeding or any claim, issue or matter therein, if they acted honestly and in good faith with a view to our best interests, and in the case of a criminal or administrative proceeding that is enforced by a monetary penalty, such persons had reasonable grounds for believing that their conduct was lawful. With the leave of the court, we also hasindemnify such persons to the fullest extent permitted by applicable law against all expenses, judgments, fines and amounts paid in settlement actually and reasonably incurred by them or on their behalf if they are, or are threatened to be made, a party to or a participant in any proceeding by us or in our right to procure a judgment in our favor, provided that such persons acted honestly and in good faith with a view to our best interests, and in the case of a criminal or administrative proceeding that is enforced by a monetary penalty, such persons had reasonable grounds for believing that their conduct was lawful. To the extent that such persons are a party to or a participant in and are successful (on the merits or otherwise) in defense of any proceeding or any claim, issue or matter therein, we will indemnify them against all expenses actually and reasonably incurred in connection with the proceedings. To the extent permitted by applicable law, if such persons are not wholly successful in such proceeding but are successful, on the merits or otherwise, in defense of one or more but less than all claims, issues or matters in such proceeding, we will indemnify them against all expenses actually and reasonably incurred in connection with (a) each successfully resolved claim, issue or matter and (b) any claim, issue or matter related to any such successfully resolved claim, issuer or matter.

We also have director and officer insurance policies that will indemnify itsinsure our officers and directors against non-indemnifiableunindemnifiable costs, charges and expenses, and may also enable the Registrantus to recover some or all of any future amounts paid pursuant to the registrant’sour indemnity obligations.

The attached Exhibit Index is incorporated herein by reference.

II-2

Insofar as indemnification(a) The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) To include any prospectus required by Section 10(a)(3) of the Securities Act of 1933;

(ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Securities and Exchange Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20 percent change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement;

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in this registration statement.

Provided,however, that paragraphs (a)(1)(i), (a)(1)(ii) and (a)(1)(iii) above do not apply if the registration statement is on Form S-3 or Form F-3 and the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Securities and Exchange Commission by the registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement or is contained in a form of prospectus filed pursuant to Rule 424(b) that is a part of the registration statement.

(2) That, for liabilities arisingthe purpose of determining any liability under the Securities Act of 1933, mayeach such post-effective amendment shall be permitteddeemed to directors, officers and controlling persons of the Registrant pursuantbe a new registration statement relating to the provisions set forth in Item 15 above, or otherwise,securities offered therein, and the Registrant has been advisedoffering of such securities at that intime shall be deemed to be the opinioninitialbona fide offering thereof.

(3) To remove from registration by means of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrantpost-effective amendment any of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered which remain unsold at the Registrant will, unlesstermination of the offering.

(b) The undersigned registrant hereby further undertakes that, for the purpose of determining liability under the Securities Act of 1933 to any purchaser:

(1) Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the opinionregistration statement; and

(2) Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of its counsela registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii), or (x) for the matter has been settledpurpose of providing the information required by controlling precedent, submitsection 10(a) of the Securities Act of 1933 shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initialbona fide offering thereof.Provided,however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated

II-3

or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a courtpurchaser with a time of appropriate jurisdiction the question whethercontract of sale prior to such indemnification by it is against public policy as expressedeffective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(c) That, for the purpose of determining liability of the registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be governedconsidered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the final adjudicationundersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(d) The undersigned registrant hereby undertakes that: (i) for purposes of determining any liability under the Securities Act of 1933, the information omitted from the form of prospectus filed as part of the registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of the registration statement as of the time it was declared effective; and (ii) for the purpose of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such issue.securities at that time shall be deemed to be the initialbona fide offering thereof.

(e) The undersigned Registrantregistrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the Registrant’sregistrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initialbona fide offering thereof.

The(f) If and when applicable, the undersigned Registrantregistrant, hereby undertakes:

(1) Toundertakes to file during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

PROVIDED, HOWEVER, that paragraphs (1)(i), (1)(ii) and (1)(iii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the Registrant pursuant to

Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

(2) That,an application for the purpose of determining any liabilitythe eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act in accordance with the rules and regulations prescribed by the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment anyExchange Commission under Section 305(b)(2) of the securities being registered which remain unsold at the termination of the offering.Act.

(4) That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser:

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrantregistrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the city of Bedford, state of Massachusetts, on October 9, 2008.April 3, 2012.

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS that each individual whose signature appears below constitutes and appoints Daniel J. Lyne and Robert L. Bowen, and each of them, his or her true and lawful attorneys-in-fact and agents with full power of substitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign any and all amendments to this Form S-3, including post-effective amendments, and to file the same, with all exhibits thereto and all documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents or any of them, or his, her or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

II-5

Pursuant to the requirements of the Securities Act of 1933, this Form S-3registration statement has been signed below by the following persons on behalf of the Registrant and in the capacities and on the dates indicated.indicated:

II-6

EXHIBIT INDEX