Osisko Buys Back a 1% Royalty Interest on Canadian Malartic Property

MONTREAL, QUEBEC -- (Marketwire) -- 08/05/11 -- Osisko Mining Corporation ('Osisko')(TSX: OSK)(FRANKFURT: EWX), is pleased to announce that it has purchased back a 1% royalty interest from Geoconseils Jack Stoch Limitee in consideration for the issuance of 460,000 common shares of Osisko. This royalty was encumbering a portion of the Canadian Malartic and Barnat deposits and is part of a 2.5% Gross Metal Royalty interest that was granted as a result of the acquisition of certain claims of the Canadian Malartic property in March 2006.

Sean Roosen, President and Chief Executive Officer, noted: 'The partial buy back of the Stoch royalty allows us to reduce our cash costs and provides our shareholders with an increased participation in a rising gold market'.

Following this purchase, only 60% of the recoverable gold ounces at the Canadian Malartic mine will be subject to a 1.5% Net Smelter or Gross Metal Royalty, based on the most recently published reserve estimates (see March 31, 2011 press release).

Second Quarter 2011 Results Conference Call

Osisko will host a conference call on Friday, August 12 at 10:00 AM EDT, where senior management will discuss the financial results and provide an update of the Company's activities. Those interested in participating in the conference call should dial in at 416-981-9000 (Toronto local and international), or 1-800-755-1805 (North American toll free). An operator will direct participants to the call.

About Osisko Mining Corporation

Osisko Mining Corporation operates the Canadian Malartic Gold Mine in Malartic, Quebec and is pursuing exploration on a number of properties, including the Hammond Reef Gold Project in Northern Ontario.

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 including, without limitation, increasing of throughput at the mill to achieve design capacity, improving mill feed grade, maintaining recovery rates and increasing gold production. Although the Corporation believes the expectations expressed in such forward-looking statements are based on reasonable assumptions, including, without limitation that the diligent ongoing optimizing of its operations will be achieved and will, accordingly, improve its operating performance, 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, the Corporation's limited experience with production and development stage mining operations, uninsured risks, regulatory changes or sanctions, defects in titles, 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 operation costs, 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.

Contacts:

John Burzynski

Vice-President Corporate Development

(416) 363-8653
www.osisko.com


Sylvie Prud'homme

Director of Investor Relations

(514) 735-7131

Toll Free: 1-888-674-7563