OSISKO INTERSECTS 1.20 g/t Au OVER 86.9 METRES AT JEFFREY ZONE

Montreal, Quebec, September 11, 2009 - Osisko Mining Corporation (�Osisko�, OSK - TSX, EWX - Deutsche Boerse) is pleased to announce the initial results from the 2008 drill program targeting the Jeffrey Zone on the Malartic CHL property, currently under option from Golden Valley Mines Ltd. (GZZ:TSX-V).

The Jeffrey Zone is a gold-mineralized prospect located at the southern extremity of the CHL porphyry, approximately 3.5 km east of the center of the Canadian Malartic deposit, currently under development by Osisko. The Jeffrey Zone was tested with a series of nineteen (19) drill holes (CHL08-2063 to CHL08-2090 for 5,601m) located along drill sections spaced 50 metres apart over a 400 x 100 metre area. All of the holes in the Jeffrey Zone were oriented to the north or south, perpendicular to the regional E-W fabric and were inclined from -45 to -78 degrees.

Most of the holes intersected mineralization along each section drilled. The most significant near-surface drill results include 86.9m averaging 1.20g/t Au (CHL08-2079) including 6.0m averaging 7.35g/t Au. The depth extension of the Jeffrey Zone was also confirmed with drill intercepts of 33.5m averaging 0.78g/t Au (CHL08-2088) and 12.6m averaging 1.14g/t Au (CHL08-2090).  Assay highlights from the nineteen new drill holes are summarized in the table below:

Mineralization at the Jeffrey Zone consists of disseminated pyrite-gold in potassic-altered quartz-feldspar porphyry dikes in contact with a predominately ultramafic flow sequence, and in lesser gabbro and sedimentary units. Narrower, higher grade mineralization is hosted in quartz veins or silicified porphyry or talcose ultramafic schists.

Presently the Jeffrey Zone has been traced continuously by surface Diamond drilling over a strike length of 400 metres and a depth of 90 to 150 metres.  True average width is estimated at 42 metres. The mineralized system remains open to the east and at depth, as was highlighted from the results from a 9-hole, 2,400 metre program completed in 2007 (see April 17, 2008 press release), which produced significant intersections as far as 375 metres further to the east. Significant near-surface drill results from the 2007 program include 53.9m averaging 1.25 g/t Au (CHL07-2022) and 40.5m averaging 1.39g/t Au (CHL07-2021).

Results from the 2007 and 2008 drill programs warrant a follow-up definition drill program to be completed with the objective of issuing, if warranted, a NI 43-101 resource estimate. Due to very wet ground conditions in the area of the Jeffrey Zone, this definition drill program is planned for the win ter of 2009-2010.

Currently the last remaining holes from the 2008 program are being logged and sampled with additional results to be released in the coming weeks for the reconnaissance drilling completed along the prospective CHL porphyry-volcanic contact and the Shaft Zone.

Osisko has the right to acquire a 70% interest in the Malartic CHL Property in consideration for $150,000 in cash payments over a four year period (total amount paid to date) and by completing a minimum $2,000,000 in exploration work over a four year period. Upon earning its 70% interest, Golden Valley will maintain a free-carried interest of 30% to production. Presently, option/joint venture partner and operator Osisko has completed 19,746 metres (101 drill holes) on the property in 2008 and 15 holes totaling 6,544 metres in 2007.

All NQ or HQ core assays reported above were obtained by standard 50 g fire assaying-AA finish or gravimetric finish at ALS Chemex laboratories in Val d' Or, Quebec. Reported weighted averages were calculated using a minimum of 0.50 g/t Au over successive maximum intervals of 20 metres with no upper cut-off of individual assays.  Intersected drifts or lost core within mineralized intersections were incorporated as blank intervals.

Osisko Mining Corporation is currently developing the Canadian Malartic gold deposit and evaluating adjacent areas for a large-scale open pit, bulk-tonnage mining operation. The Canadian Malartic deposit currently represents one the biggest gold reserves in Canada for a single deposit, and is still growing through ongoing drilling on new mineralized zones. Current reserves for the Canadian Malartic property are 6.28 million ounces, plus (including the Barnat deposit) a measured and indicated resource of 3.65 million ounces and an inferred resource of 0.84 million ounces. Mr. Robert Wares, P. Geo. and Executive Vice-President of Osisko, is the Qualified Person who has rev iewed this news release and is responsible for the technical information reported herein, including verification of the data disclosed including the sampling, analytical and test data underlying the technical information.

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 on the stated resources 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�, �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 comm ercial 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.

For further information please contact:

Osisko Mining Corporation
John Burzynski
Vice-Pre sident Corporate Development
Tel.: (514) 735-7131
www.osisko.com

or

Osisko Mining Corporation
Sylvie Prud'homme
Investor Relations
Tel.: (514) 735-7131
Toll Free: 1-888-674-7563

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