MONTREAL, QUEBEC--(Marketwire - Sept. 8, 2011) - Osisko Mining Corporation ("Osisko") (TSX:OSK)(FRANKFURT:EWX) is pleased to announce results from the spring and summer 2011 drill program at the Canadian Malartic and the Malartic CHL properties, located adjacent to Osisko's 100%-owned Canadian Malartic gold mine.

The drill program was focused on the Barnat Extension (Mammoth) area and intersected new mineralization, located either within or immediately outside the currently designed engineered pit over the eastern portion of the Barnat deposit. All of these mineralized intersections were drilled after the publication of the latest resource/reserve estimate (see March 31, 2011 press release) and are therefore not included in the current gold inventory. Highlights include 172.5 metres averaging 1.23 g/t Au, 126.5 metres averaging 1.70 g/t Au and 111.5 metres averaging 1.24 g/t Au, as well as higher grade intersections such as 3.2 metres averaging 42.05 g/t Au (uncut). Assay results for significant intersections are summarized in the table below:

BA-series holes are located on the Canadian Malartic property and CHL-series holes are located on the Malartic CHL property. The drill results indicate mineralization from the Barnat Zone extends further east of the eastern limit of the current pit design, towards the Jeffrey Zone on the Malartic CHL property.

The resource estimate on the Jeffrey Zone, calculated from data of the 2009-2010 definition drill program, is approaching completion and results will be disclosed before the end of the third quarter 2011. Abitibi Royalties Inc. owns a 30% free-carried interest in the Malartic CHL property.

All NQ 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 drill core weighted averages were calculated using a minimum of 0.35 g/t Au over successive intervals of 20 metres. The lengths of mineralized intervals of less than 20 metres were minimized, and an upper cut-off of 30 g/t Au was applied to individual assays where indicated. Intervals containing individual assays that are greater than six times the average of the interval are included separately. Intersected drifts or lost core within mineralized intersections were incorporated as blank intervals.

Osisko follows strict QA-QC protocol measures in keeping with industry standards and regulatory reporting requirements. Mr. Robert Wares, P. Geo. and Executive Vice-President of Osisko is the Qualified Persons 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 on the stated resources will lead to mineral reserves that can be mined economically.