Osisko Tables Environmental Impact Study for Its Canadian Malartic Project

MONTREAL, QUEBEC--(Marketwire - Sept. 5, 2008) - Osisko Mining Corporation ("Osisko") (TSX: OSK.TO)(FRANKFURT: EWX.F) submitted yesterday its environmental impact assessment study for its Canadian Malartic mining project to Quebec's Ministere du Developpement durable, de l'Environnement et des Parcs (MDDEP).

"We're very pleased to reach this major milestone in the regulatory approval process." said Mr. Sean Roosen, President and CEO of Osisko. "To conduct this study over the past year we've had to call on many experts in many fields, and we are extremely proud of the result. From the start of our project, we have been committed to optimizing the positive impacts of our project for the town of Malartic, the Abitibi-Timiskaming region and the Province of Quebec, while striving to minimize impacts on the physical and human environment. We are working diligently as responsible corporate citizens to achieve successful integration between the two."

The impact study concludes that given the chosen site for mining infrastructure, the selected technology, and the open communication with the various stakeholders, the Canadian Malartic project would have a minimal impact on the environment and the population and well within acceptable industrial norms. Moreover, Osisko has demonstrated with its work to date that it is a major partner in the responsible development of Malartic and its surrounding area. The impact study also underscores significant spin-offs the project would have on the local and regional economy. Highlights of the impact study are appended to this press release.

Osisko remains committed to providing the population of Malartic with thorough and transparent information on the evolution of the Canadian Malartic project. With this goal in mind, the Company will send information to Malartic residents over the coming weeks summarizing the study and explaining the main findings.

Copies of the study will be available for consultation at the Osisko community outreach office, located at 864 rue Royale in Malartic, and at the Malartic Town Hall. The study is also available online, along with the supporting documents, on the Osisko website at: www.osisko.com.

Moving Forward

The study will be reviewed by Quebec government authorities to establish compliance with MDDEP guidelines. During this time and until the study is declared admissible by the MDDEP, Osisko will answer any questions received from the government and provide additional information as requested.

The BAPE public hearing process will start following the MDDEP's review of the study, leading to a report that will be submitted for approval to members of the Quebec Cabinet.

Cautionary Note: the Canadian Malartic mineral resource is not a mineral reserve, and the economic feasibility of the project has not been demonstrated. The mineral resource estimate for the Canadian Malartic project includes an inferred resource. This estimate is considered too speculative from a geological standpoint to apply economic parameters that would make it possible to consider it a mineral reserve. Moreover, there is no assurance that subsequent work will result in an economically mineable mineral reserve.

Forward-looking statements

Certain statements contained in this press release may be deemed "forward-looking statements". All statements in this release, other than statements of historical fact, that address events or developments that the Corporation expects to occur, are forward-looking statements. Forward-looking statements are statements that are not historical facts and are generally, but not always, identified by the words "expects", "plans", "anticipates", "believes", "intends", "estimates", "projects", "potential", "scheduled" and similar expressions, or that events or conditions "will", "would", "may", "could" or "should" occur. Although the Corporation believes the expectations expressed in such forward-looking statements are based on reasonable assumptions, including, without limitation that all technical, economical and financial conditions will be met in order to put the Canadian Malartic Project into commercial production, such statements are not guarantees of future performance and actual results may differ materially from those in forward-looking statements. Factors that could cause the actual results to differ materially from those in forward-looking statements include gold prices, access to skilled consultants, mining development and mill production personnel, results of exploration and development activities, the Corporation's limited experience with production and development stage mining operations, uninsured risks, regulatory changes, defects in title, availability of personnel, materials and equipment, timeliness of government approvals, actual performance of facilities, equipment and processes relative to specifications and expectations, unanticipated environmental impacts on operations, market prices, continued availability of capital and financing and general economic, market or business conditions. These factors are discussed in greater detail in the Corporation's most recent Annual Information Form filed on SEDAR, which also provides additional general assumptions in connection with these statements. The Corporation cautions that the foregoing list of important factors is not exhaustive. Investors and others who base themselves on the Corporation's forward-looking statements should carefully consider the above factors as well as the uncertainties they represent and the risk they entail. The Corporation believes that the expectations reflected in those forward-looking statements are reasonable, but no assurance can be given that these expectations will prove to be correct and such forward-looking statements included in this press release should not be unduly relied upon. These statements speak only as of the date of this press release.

APPENDIX: HIGHLIGHTS OF THE IMPACT STUDY

Human Aspect

Particular attention was given to the human aspect of the project's impacts. Sector studies focused on:

- Health

- Economy

- Quality of life (noise, vibrations, visual aspect, traffic)

- Project acceptability

When consulted by Osisko, the local population voiced its concerns about noise, vibrations, air quality and visual impacts. The study outlines the precautions and measures integrated into the project by Osisko to minimize any impacts on the quality of life for the citizens of Malartic and the non-organized territory of Lac-Fouillac. The sector study on health concludes that the project poses no threat to surrounding populations, notably in terms of airborne metal emissions.

From an economic standpoint, a little more than a third of Osisko's mine construction and development expenditures, totalling 540 million dollars, would be made in the Malartic and the Abitibi-Timiskaming region. Osisko will implement a policy to maximize the local and regional acquisition of goods and services, as well as the hiring of its workforce from the Malartic and the Abitibi- Timiskaming region. While in production, Osisko expects that 349 of the 392 direct jobs to be created at the potential mine would be occupied by residents of Malartic and the surrounding areas. Osisko has also recently created and financed the "Fonds Essor Malartic Osisko" (FEMO), a sustainability fund designed to ensure long-term benefits for Malartic created by Osisko's presence in the region.

Finally, the study highlights the structuring effect that the Canadian Malartic project would have on the development of municipal lands and on the start-up of environmental projects at the regional level. Thus, it would give the municipality of Malartic a stronger voice on matters of sustainable development within the Vallee-de-l'Or Regional County Municipality (MRC).

Physical Environment

Impacts on the physical environment were the focus of several sector studies dealing with:

- Air

- Water

- Soil

- Vegetation & Wildlife

Overall, most of the expected impacts of the Canadian Malartic gold mining project have been deemed minor, mainly due to the following factors:

- There will be some overlap between the proposed mining facilities and existing installations from the former Canadian Malartic and East Malartic mines, which were closed in 1965 and 1983 respectively;

- Osisko intends to locate the new facilities within the confines of watersheds already impacted by previous operations;

- The environment of the proposed new mine has already been disturbed by decades of mining operations between 1935 and 1983, and as such, the new project does not involve major impacts from a biological standpoint: terrestrial and aquatic wildlife populations are not widespread or diverse;

- None of the areas to be affected are of important impact for Quebec's wildlife or vegetation, and although some areas will be deforested, this clearing will be compensated for at the end of the project by the reclamation and reforestation of the tailings pond and waste pad areas.

Monitoring

In the event the Canadian Malartic project is brought into commercial production, Osisko is committed to implementing all the mitigation measures laid out in the impact study, without exception, in addition to all proposed follow-up and monitoring programs. Osisko intends to implement a strict monitoring program of groundwater levels from the start-up of mining operations and would extend the program until the end of the mine closure process. Osisko would also prepare a groundwater contingency plan that could be implemented to prevent or minimize any potential impacts on the natural environment, or any perceived impact on local water supply. In keeping with this precautionary spirit, Osisko would follow the same approach for dust, noise and vibrations.

Contacts

Jean-Sebastien David
Osisko Mining Corporation
Vice-President, Sustainable Development
514-735-7131
david@osisko.com
www.osisko.com

Sylvie Prud'homme
Osisko Mining Corporation
Investor Relations
514-735-7131
Toll Free: 1-888-735-7131
prudhomme@osisko.com