(Montreal, May 17, 2012) Osisko Mining Corporation (the "Company" or "Osisko") (OSK: TSX, EWX: Deutsche Boerse) is pleased to report that the Canadian Malartic mill has been returned to operational status as of 10 pm Wednesday evening.  The grinding circuit is currently operating on a reduced basis using bypass feed with three of the four cyclone sets and two of three ball mills, as well as the SAG.  Work is progressing on the repairs to the number 4 cyclone set, which is expected to be returned to operation within one weeks time.  Recommissioning of the number 4 cyclone set will allow the third ball mill to be returned to operation. The primary and secondary crushers are undergoing scheduled maintenance and are expected to be returning to operation by Saturday.

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 Osisko 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, consequences of this incident on operations at Canadian Malartic and resumption of operations. Although Osisko believes the expectations expressed in such forward-looking statements are based on reasonable assumptions, including, without limitation, that all technical conditions will be met in order to proceed diligently with resumption of milling activities at Canadian Malartic however 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 access to skilled consultants, mining development and construction personnel, Osisko's limited experience with production and development of operations, uninsured risks, regulatory framework and changes, availability of personnel, materials and equipment, actual performance of facilities, equipment and processes relative to specifications and expectations, continued availability of capital and financing and general economic, market or business conditions. These factors are discussed in greater detail in Osisko's most recent Annual Information Form and in the most recent Management Discussion and Analysis filed on SEDAR, which also provide additional general assumptions in connection with these statements. Osisko cautions that the foregoing list of important factors is not exhaustive. Investors and others who base themselves on forward-looking statements should carefully consider the above factors as well as the uncertainties they represent and the risk they entail. Osisko 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.