Denison Mines Corp. Comments on Recent Market Activity

TORONTO, ONTARIO--(Marketwire - Sept. 18, 2012) - Denison Mines Corp. ("Denison" or the "Company") (TSX:DML)(NYSE MKT:DNN)(NYSE Amex:DNN), in response to a request of the Investment Industry Regulatory Organization of Canada (IIROC) on behalf of the Toronto Stock Exchange, confirms that there are no material undisclosed corporate developments that might account for the increased trading activity of the Company's shares today. Denison does not otherwise comment on market activity.

About Denison

Denison Mines Corp. is a uranium exploration and development company with interests in exploration and development projects in Saskatchewan, Zambia and Mongolia. As well, Denison has a 22.5% ownership interest in the McClean Lake uranium mill, located in northern Saskatchewan, which is one of the world's largest uranium processing facilities. Denison's exploration project portfolio includes the world-class Phoenix deposit located on its 60% owned Wheeler River project also in the Athabasca Basin region of Saskatchewan.

Denison is engaged in mine decommissioning and environmental services through its Denison Environmental Services (DES) division. Denison is also the manager of Uranium Participation Corporation (TSX-U), a publicly traded company which invests in uranium oxide in concentrates and uranium hexafluoride.

Cautionary Statements

Certain information contained in this press release constitutes "forward-looking information", 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.

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", "be achieved" or "has the potential to".

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. Denison believes that the expectations reflected in this forward-looking information are reasonable but no assurance can be given that these expectations will prove to be correct and such forward-looking information included in this press release should not be unduly relied upon. This information speaks only as of the date of this press release. In particular, this press release may contain forward-looking information pertaining to the following: the estimates of Denison's mineral resources; capital expenditure programs; estimated production costs, exploration and development expenditures and reclamation costs; expectations of market prices and costs; supply and demand for uranium; possible impacts of litigation and regulatory actions on Denison; exploration, development and expansion plans and objectives; Denison's expectations regarding raising capital and adding to its mineral resources through acquisitions and development; and receipt of regulatory approvals, permits and licences and treatment under governmental regulatory regimes.

There can be no assurance that such statements will prove to be accurate, as Denison's actual results and future events could differ materially from those anticipated in this forward-looking information as a result of those factors discussed in or referred to under the heading "Risk Factors" in Denison's Annual Information Form dated March 28, 2012, available at http://www.sedar.com, and in its Form 40-F available at http://www.sec.gov, as well as the following: global financial conditions, the market price of Denison's securities, volatility in market prices for uranium; ability to access capital, changes in foreign currency exchange rates and interest rates; liabilities inherent in mining operations; uncertainties associated with estimating mineral reserves and resources and production; uncertainty as to reclamation and decommissioning liabilities; failure to obtain industry partner and other third party consents and approvals, when required; delays in obtaining permits and licenses for development properties; competition for, among other things, capital, acquisitions of mineral reserves, undeveloped lands and skilled personnel; public resistance to the expansion of nuclear energy and uranium mining; uranium industry competition and international trade restrictions; incorrect assessments of the value of acquisitions; property title risk; geological, technical and processing problems; the ability of Denison to meet its obligations to its creditors; actions taken by regulatory authorities with respect to mining activities; the potential influence of or reliance upon its business partners, and the adequacy of insurance coverage.

Accordingly, readers should not place undue reliance on forward-looking statements. These factors are not, and should not be construed as being, exhaustive. Statements relating to "mineral reserves" or "mineral resources" are deemed to be forward-looking information, as they involve the implied assessment, based on certain estimates and assumptions that the mineral reserves and mineral resources described can be profitably produced in the future. The forward-looking information contained in this press release is expressly qualified by this cautionary statement. Denison does not undertake any obligation to publicly update or revise any forward-looking information after the date of this press release to conform such information to actual results or to changes in Denison's expectations except as otherwise required by applicable legislation.

Cautionary Note to United States Investors Concerning Estimates of Measured, Indicated and Inferred Resources: This press release may use 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.