Osisko Intersects 191 Metres Averaging 2.16 g/t Au at South Barnat

MONTREAL, QUEBEC, Apr 20 (MARKET WIRE) --
Osisko Mining Corporation ("Osisko")(TSX: OSK)(FRANKFURT: EWX) is pleased
to announce new results from the infill drill program currently under way
at South Barnat, a separate gold mineralized zone located northeast of
the Canadian Malartic deposit. Significant drill intersections include
1.75 g/t Au over 345.5 metres (BA08-3257), 2.16 g/t Au over 191.0 metres
(BA08-3277) and 2.08 g/t Au over 106.6 metres (BA08-3316B). Higher grade
intersections include 17.21 g/t Au over 42.0 metres (including 437.0 g/t
over 1.5 m in BA08-3272), 17.12 g/t Au over 5.0 metres (BA08-3293) and
10.1 g/t Au over 23.4 metres (including 110.0 g/t over 1.5 m in
BA08-3331). Highlights from 100 new infill holes that yielded
better-than-expected results are tabled below:

Hole No. Section From (m) To (m) Length (m) Au g/t
BA08-3252 675E 108.0 203.0 95.0 2.01
BA08-3257 525E 42.5 388.0 345.5 1.75
including 59.0 60.0 1.0 57.30
including 198.0 199.5 1.5 29.30
including 264.0 265.5 1.5 28.90
BA08-3259 225E 15.0 142.2 127.2 1.94
BA08-3271 525E 10.9 33.9 23.0 7.23
including 21.5 23.0 1.5 55.80
And 94.0 99.5 5.5 75.85
And 109.5 194.3 84.8 1.54
BA08-3272 525E 11.0 53.0 42.0 17.21
including 35.5 37.0 1.5 437.0
And 104.0 232.0 128.0 1.19
BA08-3277 675E 143.5 334.5 191.0 2.16
including 274.0 275.5 1.5 26.70
including 283.5 285.0 1.5 32.20
BA08-3287B 125E 18.3 51.0 32.7 1.62
And 170.0 194.5 24.5 5.19
BA08-3290 275E 12.5 77.3 64.8 4.39
including 21.5 23.0 1.5 84.00
BA08-3293 675E 69.0 82.5 13.5 3.36
And 230.5 235.5 5.0 17.12
And 269.0 328.0 59.0 3.38
And 377.0 522.0 145.0 1.09
BA08-3310 675E 146.5 239.0 92.5 2.09
BA08-3316B 625E 161.0 267.6 106.6 2.08
BA08-3317 225E 18.5 47.0 28.5 1.02

All other drill holes in the range between BA08-3251 and BA08-3350
gave results that were within expectations of the existing resource
model. The exceptionally long intersection in drill hole BA08-3257 is a
result of the hole cutting the entire width of the South Barnat zone on
section 525E over a true width of about 75 metres and then following the
down-dip projection of the Sladen extension on the south side of the
fault for approximately 200 metres. Results from drill hole BA08-3287B
and BA08-3317 are of particular significance as these intersections
(including the deeper one in -3287B) represent new mineralization located
about 100 metres north of the South Barnat zone. Assay results for
further holes at South Barnat are being processed.

The definition drill program is focused on an 850 metre-long grid
oriented northwest-southeast with drill sections spaced 25 metres apart.
All holes on this grid are inclined 45 to 75 degrees to the northeast or
southwest. True widths of most the mineralized intersections reported
above are 40 to 70 percent of the drilled intersections. A NI 43-101
compliant inferred resource estimate of 2.0 million ounces for South
Barnat was released on January 26, 2009 and the technical report was
filed on SEDAR on February 17, 2009. The current definition drill program
will lead to a NI 43-101 compliant, in-pit Measured and Indicated
resource estimate for South Barnat, to be released in May 2009.

Drilling to date suggests that the minimum strike length of the South
Barnat Zone is 850 metres with an average true width between 30 and 120
metres. The mineralized zone is open along strike to the east, where it
merges with the old East Malartic Mine and where recent drilling has
indicated a possible extension over an additional 360 metres (see January
13, 2009 press release). South Barnat extends to depths of 250 to 400
metres in the southeastern portion, where the system is still open at
depth. Estimated depth in the northwestern third of the deposit is 130 to
200 metres.

Mineralization in the South Barnat Zone is located to the north and south
of the old Barnat and East Malartic mine workings, along the southern
edge of the Cadillac fault. The disseminated gold mineralization
comprises multiple subvertical, tabular subzones hosted in silicified
greywackes of the Pontiac Group south of the fault contact. North of the
fault, mineralization is hosted in both porphyry dykes and schistose,
carbonatized and biotitic ultramafic rocks north. Porphyry dykes also
host late quartz veins containing visible gold.

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 Corp. is currently developing the Canadian Malartic gold
deposit and adjacent mineralized zones into a large-scale open pit,
bulk-tonnage mining operation. The Company is well-funded and is carrying
out an aggressive definition drilling, exploration and development
campaign. A NI 43-101 compliant, 7.7 million ounce gold Measured and
Indicated global resource on the main Canadian Malartic gold deposit was
released on September 8, 2008 and the technical report has been filed on
SEDAR. This includes a NI 43-101 compliant, 6.3 million ounce gold
Reserve estimate released in the Feasibility Study on the main Canadian
Malartic gold deposit on November 25, 2008, for which the technical
report has been filed on SEDAR. These estimates did not include the South
Barnat Zone or any other mineralized zone located outside the main
deposit that is currently being evaluated by Osisko.

Mr. Robert Wares, P. Geo. and Executive Vice-President 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 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 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 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.

Contacts:
Osisko Mining Corporation
John Burzynski
Vice-President Corporate Development
514-735-7131

Osisko Mining Corporation
Investor Relations:
Daniel Boase
416-742-5600
Toll Free: 1-866-580-8891
www.osisko.com

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