MONTREAL, QUEBEC--(Marketwire - Aug. 11, 2011) - Osisko Mining Corporation (the "Company" or "Osisko") (News - Market indicators)(FRANKFURT:EWX) is pleased to report its review of activities and financial results for the quarter ended June 30, 2011.

Highlights

• Commencement of commercial production at Canadian Malartic on May 19, 2011
• Gold production of 46,605 ounces
• Continued progress in mill and mine ramp up
• Mine operating earnings of $1.6 million
• Loss of $23.8 million
• Withdrawal from Duparquet Project

The Canadian Malartic Mine successfully commenced commercial production on May 19, 2011, approximately six years after the first drilling conducted by Osisko at Malartic in March 2005. Commercial production was established on the first day of a 30-day period during which the mill processed 60% or better than the mill design capacity of 55,000 tonnes per day. Since introduction of ore in March, the ramp up has been successful despite the stops and starts that are normally experienced during the initial phase of a mining operation.

Sean Roosen, President and Chief Executive Officer commenting on the second quarter activities: "We are extremely proud of our team's efforts in rapidly moving Canadian Malartic from an exploration project to a producer, particularly considering the major challenges of developing a $1 billion project in an urban area."

The Canadian Malartic operations are expected to produce between 235,000 and 245,000 ounces of gold during the second semester of 2011 at an estimated cash cost of between $675-$775 per ounce. The progression is anticipated to continue in 2012 with the mine producing approximately 700,000 ounces at an estimated cash cost of $450-$500 per ounce.

Sean Roosen commenting on the forecast: "We are aiming to produce one million ounces over the next 18 months in a very favorable gold market. The expected strong margins should result in a payback of the project in slightly less than two years".

The Canadian Malartic Mine generated a $1.6 million profit during its initial 43-day operating period from the sale of 8,300 ounces. The remaining ounces produced during commercial production are in the circuit inventory. For the second quarter, Osisko incurred a loss of $23.8 million ($0.06 per share) due mainly to the write-off of Duparquet Project ($10.9 million), higher administrative costs, and expensed finance costs now that the Canadian Malartic Mine is in commercial production. The second quarter loss in 2010 amounted to $10.2 million ($0.03 per share). There were no mining operations prior to May 2011.

For the year-to-date, the loss totaled $29.1 million ($0.08 per share) compared to a loss of $10.7 million ($0.03 per share) in the corresponding period in 2010.

Canadian Malartic Mine

The Canadian Malartic Mine produced 46,605 ounces of gold in the second quarter from the treatment of 1.5 million tonnes of ore. Ore was first introduced late in March. Production statistics for the quarter are as follows:

The higher production costs are attributable to initial low grade material, normal inefficiencies experienced during a ramp up period, and industry-wide inflationary pressures.

The mine generated an operating profit of $1.6 million from the sale of 8,300 ounces. The remaining ounces are categorized in inventory. Prior to commercial production, the Company incurred a loss during the commissioning period which was capitalized.

The mine operating statement for the production period is as follows:

The mining activities have been affected by the delays in the construction of the green wall separating the mine and the residential area, the feedstock area for the wall construction, the noise levels of the mining operations and to a lesser extent the accelerated completion of the project, three months ahead of schedule. These factors necessitated earlier access to lower grade material than modeled in the feasibility, and the grade of ore treated is expected to increase throughout the second semester. Lower grade material has a significant negative impact on the unit costs. It is important to note however, that the mining grades are conforming to the reserve block model (+2% average variation), validating the extensive drilling program conducted to establish the mining reserves and plan.

The mill continues its ramp up process with scheduled shut downs for verifications, repairs and modifications. The operating statistics are as follows:

A new daily throughput record of 47,485 tonnes processed was established on August 7, 2011.

The ramp up period has demonstrated that the rock hardness is as anticipated and the crusher and ball mills are performing better than their design criteria. The ramp up has also shown that the ore's SAG impact breakage index has demonstrated lower SAG grindability. The addition of a pre-crush circuit will allow for throughput expansion to 60,000+ tpd. The units have been ordered and will be available in early 2012, with the project costs estimated at $32 million. A portable crushing unit has been installed to increase the crushing capacity in the meantime.

Exploration and Development

The Company continues to aggressively pursue growth of reserve and resource base through intensive drilling programs around the Canadian Malartic Mine, at its Hammond Reef Project and on various grass-roots projects in Eastern Canada. A total of 88,336 metres (341 holes) were drilled during the second quarter, mostly from the definition drill program at Hammond Reef.

Following an evaluation of the results from its $15 million exploration program at Duparquet, the Company decided to serve notice to Clifton Star Resources that it was withdrawing from its joint venture program. As a result, a write-off of $10.9 million was recorded in the second quarter.

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. The call will be retransmitted for 14 days with the following dial in number: 416-626-4100 or Toll-free 1-800-558-5253, access code 21534865.

Highlights from the Company's financial position are as follows (in millions of dollars):

The unaudited condensed interim consolidated financial statements and Management Discussion and Analysis for the period ended June 30, 2011 will be filed on SEDAR on August 15, 2011.

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.

Mr. Luc Lessard, P. Eng., Senior Vice-President and COO of Osisko, is the Qualified Person who has reviewed this news release and is responsible for the technical information reported herein, including verification of the data disclosed.

Cautionary Notes Concerning Estimates of Mineral Resources

This news release uses the terms measured, indicated and inferred resources as a relative measure of the level of confidence in the resource estimate. Readers are cautioned that mineral resources are not economic mineral reserves and that the economic viability of resources that are not mineral reserves has not been demonstrated. In addition, inferred resources are considered too geologically speculative to have any economic considerations applied to them. It cannot be assumed that all or any part of an inferred mineral resource will ever be upgraded to a higher category. Under Canadian rules, estimates of inferred mineral resources may not form the basis of feasibility or pre-feasibility studies or economic studies except for Preliminary Assessment as defined under NI 43-101. Readers are cautioned not to assume that that further work will lead to mineral reserves that can be mined economically.

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" 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 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 materials and equipment, timeliness of government approvals, actual performance of facilities, equipment and processes relative to specifications and expectations, unanticipated environmental impacts on operations 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.