Denison Mines Corp.: Assay Results Confirm and Significantly Exceed Previously Reported Grade Equivalent Results From

TORONTO, ONTARIO, May 25 (MARKET WIRE) --
Denison Mines Corp. (TSX: DML) (NYSE Amex: DNN) ("Denison" or the
"Company") is pleased to report that assays have been returned for the
equivalent grade results announced on April 2, 2009. The assay results
not only confirmed the equivalent down-hole probing results but
significantly increased most grades.

WR-267 previously reported equivalent grades of 15.5% eU3O8 over 2.9
metres from 408.2 metres. Split core assay grades from the same interval
were 23.3% U3O8 over 3.0 metres from 405.0 metres.

WR-268 previously reported equivalent grades of 12.5% eU3O8 over 2.4
metres from 409.5 metres and 2.7% eU3O8 over 0.5 metres from 416.9
metres. Split core assay results for the same intervals were 13.2% U3O8
over 3.0 metres from 409.5 metres and 3.0% U3O8 over 0.5 metres from
418.5 metres.

The last hole, WR-269, originally reported equivalent grades of 9.8%
eU3O8 over 1.5 metres from 407.8 metres and 2.1% eU3O8 over 1.1 m from
416.0 m. Split core assay results returned 3.5% U3O8 over 0.5 metres from
408.3 metres and 2.5% U3O8 over 1.5 metres from 415.8 metres. Due to
substantial core loss from the first mineralized interval, equivalent
grades will be reported for this intersection going forward.

These drill holes represent the last three drill holes of the winter
drilling season. The grade tabulation for all mineralized holes from the
R Zone, including summer 2008 work, is shown below.

-------------------------------------------------------------
Interval Grade
Hole # From To (m) (U3O8)
-------------------------------------------------------------
WR-249 408.00 409.35 1.35 1.7%
-------------------------------------------------------------
WR-251 386.00 388.25 2.25 0.77%
-------------------------------------------------------------
WR-253 389.70 393.70 4.00 1.40%
-------------------------------------------------------------
WR-253 395.30 395.80 0.50 1.75%
-------------------------------------------------------------
WR-258 397.50 400.00 2.50 25.70%
-------------------------------------------------------------
WR-259 397.00 401.00 4.00 19.90%
-------------------------------------------------------------
WR-260 395.70 397.20 1.50 0.25%
-------------------------------------------------------------
WR-261 408.50 410.00 1.50 7.40%
-------------------------------------------------------------
WR-261 412.50 413.00 0.50 1.55%
-------------------------------------------------------------
WR-266 414.50 415.00 0.50 7.18%
-------------------------------------------------------------
WR-267 405.00 408.00 3.00 23.30%
-------------------------------------------------------------
WR-268 409.50 412.50 3.00 13.20%
-------------------------------------------------------------
WR-268 418.00 418.50 0.50 3.0%
-------------------------------------------------------------
WR-269 408.30 408.80 0.50 3.5%
-------------------------------------------------------------
WR-269 414.80 416.30 1.50 2.5%
-------------------------------------------------------------

Note that all are reported at a 1% U3O8 cutoff except for Hole WR-260
which was reported at a 0.05% U3O8 cutoff. The slight meterage
differences in several holes are due to downhole probe levelling and the
assayed intervals are considered true depth. Holes 262, 263, 264 and 265
did not intersect significant mineralization.

2009 Summer Exploration Program

Denison is also pleased to announce that a $1.5 million (Denison's share
is $900,000) summer program has been approved by the Wheeler River Joint
Venture of which Denison is the operator holding a 60% interest (Cameco
Corp. holds a 30% interest and JCU (Canada) Exploration Company, Limited
holds the remaining 10%). The program will include at least 5,500 metres
of diamond drilling and 55 line-kilometres of DC Resistivity surveys. The
program is anticipated to begin around June 6, 2009.

The intent of the summer program will be to extend the limits of the
mineralization along the strike length as far as possible and set the
stage for a vastly expanded 2010 work program. The first hole this summer
will test the extreme southwest of the R Zone where WR-255 last year was
lost above the unconformity in the most altered sandstone encountered to
date. Subsequent holes will progress further northeast, testing for
mineralization proximal to the quartzite ridge in the centre of the known
zone around line 4000E. The width of this high-grade mineralization here
is unknown and the optimum target, near the quartzite, still has not as
yet been tested. Several holes will test extensions of the high grade
mineralization centred on line 4300 E.

The drilling in 2008 and 2009 has been focused on a total strike length
of 680 metres. Approximately half of this zone has not as yet been drill
tested and is strongly mineralized at both its northeast and southwest
extremities. Significant untested potential remains outside the zone
along strike. This project is located in the rich Athabasca Basin between
the McArthur River and Key Lake mines. This discovery has many geological
similarities to the McArthur River mineralization, but at a shallower
depth, and represents one of the most significant new discoveries in the
Athabasca Basin in several years.

Chemical analyses were completed by SRC Geoanalytical Laboratories of
Saskatoon, Saskatchewan and were a combination of geochemical and assay
methods.

The technical information contained in this press release related to the
above described exploration activities is reported and verified by
William C. Kerr, Denison's Vice President, Exploration, who is a
qualified person as defined by NI 43-101. For a description of the
quality assurance program and quality control measures applied by
Denison, please see Denison's Annual Information Form dated March 26,
2009 filed under the Company's profile on the SEDAR website.

About Denison

Denison Mines Corp. is a premier intermediate uranium producer in North
America, with mining assets in the Athabasca Basin region of
Saskatchewan, Canada and the southwest United States including Colorado,
Utah, and Arizona. Further, the Company has ownership interests in two of
the four conventional uranium mills operating in North America today.
Denison also has a strong exploration and development portfolio with
large land positions in the United States, Canada, Mongolia and Zambia.

To view the map accompanying this release please click on the following
link: http://media3.marketwire.com/docs/DenMap.JPG

Cautionary Statements

This news release contains "forward-looking statements", within the
meaning of the United States Private Securities Litigation Reform Act of
1995 and similar Canadian legislation concerning the business, operations
and financial performance and condition of Denison.

Forward looking statements include, but are not limited to, statements
with respect to the proposed transactions announced; the development
potential of Denison's properties, including those of its joint ventures;
the future price of uranium; the estimation of mineral reserves and
resources; the realization of mineral reserve estimates, the timing and
amount of estimated future production, costs of production; capital
expenditures; success of exploration activities; permitting time lines
and permitting, mining or processing issues, currency exchange rate
fluctuations, government regulation of mining operations; environmental
risks; unanticipated reclamation expenses; title disputes or claims; and
limitations on insurance coverage. Generally, these forward-looking
statements can be identified by the use of forward-looking terminology
such as "plans", "expects" or "does not expect", "is expected", "budget",
"scheduled", "estimates", "forecasts", "intends", "anticipates" or "does
not anticipate", or "believes", or variations of such words and phrases
or state that certain actions, events or results "may", "could", "would",
"might" or "will be taken", "occur" or "be achieved".

Forward looking statements are based on the opinions and estimates of
management as of the date such statements are made, and they are subject
to known and unknown risks, uncertainties and other factors that may
cause the actual results, level of activity, performance or achievements
of Denison to be materially different from those expressed or implied by
such forward-looking statements, including but not limited to risks
related to: the need for continued cooperation by the parties to the
proposed transactions in this negotiation and execution of definitive
agreement, and performance of their obligations thereunder; unexpected
events during construction, expansion and start-up; variations in ore
grade, tonnes mined, crushed or milled; delay or failure to receive board
or government approvals; timing and availability of external financing on
acceptable terms; actual results of current exploration activities;
conclusions of economic evaluations; changes in project parameters as
plans continue to be refined; future prices of uranium and vanadium;
possible variations in ore reserves, grade or recovery rates; failure of
plant, equipment or processes to operate as anticipated; accidents,
labour disputes and other risks of the mining industry; delays in the
completion of development or construction activities, as well as those
factors discussed in or referred to under the heading "Risk Factors" in
Denison's Annual Information Form dated March 26, 2009 available at
http://www.sedar.com and its Form 40-F available at http://www.sec.gov.
Although management of Denison has attempted to identify important
factors that could cause actual results to differ materially from those
contained in forward-looking statements, there may be other factors that
cause results not to be as anticipated, estimated or intended. There can
be no assurance that such statements will prove to be accurate, as actual
results and future events could differ materially from those anticipated
in such statements. Accordingly, readers should not place undue reliance
on forward-looking statements. Denison does not undertake to update any
forward-looking statements that are incorporated by reference herein,
except in accordance with applicable securities laws. Mineral resources,
which are not mineral reserves, do not have demonstrated economic
viability. Readers should refer to the Annual Information Form and the
Annual Report on Form 40-F of Denison for the year ended December 31,
2008 and other continuous disclosure documents filed since December 31,
2008 available at http://www.sedar.com, for further information relating
to their mineral resources and mineral reserves.

Cautionary Note to United States Investors Concerning Estimates of
Measured, Indicated and Inferred Resources: If this news release uses the
terms "Measured", "Indicated" and "Inferred" Resources. United States
investors are advised that while such terms are recognized and required
by Canadian regulations, the United States Securities and Exchange
Commission does not recognize them. "Inferred Mineral Resources" have a
great amount of uncertainty as to their existence, and as to their
economic and legal feasibility. 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 other economic studies. United
States investors are cautioned not to assume that all or any part of
Measured or Indicated Mineral Resources will ever be converted into
Mineral Reserves. United States investors are also cautioned not to
assume that all or any part of an Inferred Mineral Resource exists, or is
economically or legally mineable.

Contacts:
Denison Mines Corp.
Ron Hochstein
President and Chief Executive Officer
(416) 979-1991 Extension 232

Denison Mines Corp.
James R. Anderson
Executive Vice President and Chief Financial Officer
(416) 979-1991 Extension 372
(416) 979-5893 (FAX)
www.denisonmines.com

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