DML.TO · 2018-06-06 12:00:00

Denison Announces Summer Drilling Plans FOR Wheeler River and Reports Winter Assay Results

Drill Results

Denison Mines Corp.

1100 – 40 University Ave

Toronto, ON M5J 1T1

www.denisonmines.com

@DenisonMinesCo

PRESS RELEASE

DENISON ANNOUNCES SUMMER DRILLING PLANS

FOR WHEELER RIVER AND REPORTS WINTER ASSAY RESULTS

Toronto, ON – June 6, 2018 Denison Mines Corp. (“Denison” or the “Company”) (TSX: DML) (NYSE MKT:

DNN) (NYSE American: DNN) is pleased to announce summer 2018 drilling plans, and report assay results

from the winter 2018 drilling program, for the Comp any’s 63.3% owned Wheeler River project in northern

Saskatchewan.

Summer 2018 Drilling Program

The summer 2018 diamond drilling program for Wheeler River is scheduled to commence this week and is

expected to include approximately 20,500 metres in 28 drill holes. The drilling program is planned to focus

on the following target areas:

• K-North - Follow-up of high-grade uranium mineralization discovered during the winter 2018 drilling

program at 600 metres and 1 kilometre to the northeast of the Gryphon uranium deposit (see Winter

2018 Assay Highlights below).

• High-Priority Regional - Testing of high-priority targets along known fer tile trends (Q Central, K-

West) and reconnaissance exploration of high-priori ty targets generated from previous ground

geophysical surveys (K-South and Q South).

• Gryphon Unconformity - Testing of targets immediately along strike of the Gryphon deposit at the

sub-Athabasca unconformity, including extensions of the E series lenses to the northeast and the

up-plunge extents of the D series lenses to the southwest.

Dale Verran, Vice President Exploration of Denison commented, “The summer 2018 drilling program

will largely be results driven, focused on high-pri ority regional targets outside of the immediate

Gryphon resource area, and will include both the fo llow-up of high-grade mineralization and the

testing of geophysical anomalies on geologically fa vourable trends. With 3 drill rigs turning on the

project we are looking forward to a productive summ er with the potential to deliver the next

discovery at Wheeler River.”

A location map of the summer 2018 drilling target areas is provided in Figure 1.

Winter 2018 Assay Highlights

Chemical assay (“U 3O8”) results have been received for the Wheeler River winter 2018 drilling program,

which included 21,153 metres of drilling in 29 diamond drill holes. The assay results were on average 26%

higher , in terms of combined grade and thickness, than th e preliminary equivalent uranium (“eU 3O8”)

results reported previously (see Denison’s press release dated April 18, 2018). The program was focused

on step-out drilling from the Gryphon deposit and regional exploration along the K-North and K-West trend.

• Regional Exploration: Assay results confirmed high-grade intercepts from reconnaissance drill

holes targeting the sub-Athabasca unconformity, to the northeast of Gryphon, along the K-North

trend. Highlight assay results include:

a. 1.4% U 3O8 over 5.5 metres , located 600 metres northeast of Gryphon, including 7.2%

U3O8 over 1.0 metre in drill hole WR-704; and

b. 1.1% U 3O8 over 3.0 metres , located 1 kilometre northeast of Gryphon, including 2.8%

U3O8 over 1.0 metre in drill hole WR-710D1.

The results confirm the continuation of the Gryphon mineralizing system to the northeast, and

highlight the potential for the discovery of an add itional high-grade uranium deposit within the

basement or at the unconformity along strike of Gryphon.

• Gryphon Exploration: Multiple basement uranium intercepts were confirmed from step-out drilling

on 50 to 100 metre centres immediately along strike to the northeast of the Gryphon deposit. Assay

highlights from the Gryphon step-out drilling include:

a. Intercepts of upper basement mineralization exte nding the E series lenses to the northeast:

2.9% U 3O8 over 1.5 metres in drill hole WR-696; 1.2% U 3O8 over 1.5 metres in drill hole

WR-709; and 0.29% U 3O8 over 3.0 metres in drill hole WR-702; and

b. Intercept of basement mineralization, 100 metres along strike to the northeast of the

previous down-plunge extent of A series mineralization for the Gryphon deposit, including:

0.85% U 3O8 over 5.0 metres, including 2.6% U 3O8 over 1.0 metre in drill hole WR-698.

The results confirm potential to continue to expand the Gryphon mineral resource outside of the

current extents of the deposit.

Comprehensive drilling tables of composited assay r esults are provided in Table 1 and 2 below. The

location of the drill holes and the highlight assay results are shown in Figure 2.

Table 1: Composited assay results from the winter 2018 regional exploration drilling program.

Drill Hole From (m) To (m) Length (m) 5 U 3O8 (%) 1,2,4

Previously

Reported

eU 3O8 Result 6

Zone

WR-697D1 557.7 558.7 1.0 0.09 0.09% / 1.0 m

K-North - 400 m

NE of Gryphon and 665.0 666.0 1.0 0.16 0.23% / 1.0 m

WR-700 Below assay cut-off 0.11% / 1.0 m

WR-701 No significant mineralization

K-North - 600 m

NE of Gryphon WR-704 562.2 567.7 5.5 1.4 0.55% / 5.6 m

including 3 565.2 566.2 1.0 7.2 2.3% / 1.0 m

WR-705 No significant mineralization K-North - 800 m

NE of Gryphon WR-708 No significant mineralization. Anomalous geo chemistry.

WR-710 No significant mineralization.

K-North - 1 km NE

of Gryphon WR-710D1 567.3 570.3 3.0 1.1 0.94% / 3.5 m

including 3 569.3 570.3 1.0 2.8 2.7% / 1.0 m

WR-714 No significant mineralization. Anomalous geo chemistry.

K West WR-716 No significant mineralization

WR-715 No significant mineralization. Anomalous geo chemistry.

WR-717 No significant mineralization

Notes:

1. U3O8 is the chemical assay of mineralized split core samples.

2. Composited above a cut-off grade of 0.05% U3O8 unless otherwise indicated.

3. Composited above a cut-off grade of 1.0% U3O8.

4. Composites compiled using 1.0 metre minimum mineralization thickness and 2.0 metres maximum waste.

5. As the drill holes are oriented steeply toward the northwest and the unconformity mineralization is interpreted to be flat-lying, the

true thickness of the mineralization is expected to be approximately 75% of the intersection lengths.

6. Previously reported radiometric equivalent U 3O8 result (“eU 3O8”) derived from a calibrated total gamma down-hole probe (see

Denison’s press release dated April 18, 2018).

Table 2: Composited assay results from the winter 2018 Gryphon exploration drilling program.

Section Drill Hole From (m) To (m) Length (m) 5 U 3O8 (%) 1,2,4

Previously

Reported

eU 3O8 Result 6

Zone

5350GP

WR-698 777.0 782.0 5.0 0.85 0.82% / 3.9 m

A/B/C

Lens

including 3 777.5 778.5 1.0 2.6 2.1% / 1.0 m

including 3 779.5 780.5 1.0 1.3

and Merged with above interval 0.05% / 1.0 m

WR-698D1 783.4 784.4 1.0 0.05 0.06% / 1.0 m

5400GP

WR-703 806.5 809.0 2.5 0.48 0.35% / 2.3 m

and 814.0 815.0 1.0 0.09 0.08% / 1.0 m

WR-703D1 No significant mineralization

5450GP WR-707 802.5 803.5 1.0 0.23 0.15% / 1.0 m

5325GP

WR-696 Below assay cut-off 0.28% / 1.2 m

E Lens

and 595.2 596.7 1.5 2.9 2.5% / 1.3 m

including 3 595.2 596.2 1.0 4.1 3.3% / 1.0 m

and Below assay cut-off 0.06% / 1.0 m

and 624.6 625.6 1.0 0.19 0.09% / 1.0 m

and 665.0 666.0 1.0 0.30 0.42% / 1.2 m

5350GP

WR-699 No significant mineralization

WR-699D1 604.7 605.7 1.0 0.06 0.06% / 1.0 m

and 606.7 607.7 1.0 0.05

and 620.4 621.4 1.0 0.06 0.07% / 1.0 m

5400GP

WR-702 543.4 546.4 3.0 0.29 0.38% / 2.8 m

and 552.8 553.8 1.0 0.05

and 579.9 580.9 1.0 0.07

and 705.4 706.4 1.0 0.09 0.09% / 1.0 m

and 715.5 716.5 1.0 0.26 0.44% / 1.0 m

WR-702D1 556.2 557.7 1.5 0.38 0.26% / 1.0 m

5450GP WR-706 No significant mineralization

5500GP

WR-709 580.6 582.1 1.5 1.2 0.86% / 1.9 m

including 3 580.1 581.1 1.0 1.2 1% / 1.0 m

WR-709D1 No significant mineralization

5550GP WR-712 Below assay cut-off 0.09% / 1.0 m

4975GP WR-718 No significant mineralization.

D Lens

5000GP WR-713 669.0 671.0 2.0 0.09 0.16% / 2 m

5025GP WR-713D1 No significant mineralization.

5075GP

WR-711 Below assay cut-off 0.06% / 1.0 m

and 635.0 637.5 2.5 0.24 0.06% / 1.0 m

and Merged with above interval 0.46% / 1.1 m

Notes:

1. U3O8 is the chemical assay of mineralized split core samples.

2. Composited above a cut-off grade of 0.05% U3O8 unless otherwise indicated.

3. Composited above a cut-off grade of 1.0% U3O8.

4. Composites compiled using 1.0 metre minimum mineralization thickness and 2.0 metres maximum waste.

5. As the drill holes are oriented steeply toward the northwest and the unconformity mineralization is interpreted to dip moderately to

the southeast, the true thickness of the mineralization is expected to be approximately 75% of the intersection lengths.

6. Previously reported radiometric equivalent U 3O8 result (“eU 3O8”) derived from a calibrated total gamma down-hole probe (see

Denison’s press release dated April 18, 2018).

Sampling and Assay Procedures

Drill core with anomalous total gamma radioactivity (>300 counts per second using a RS-120 or RS-125

scintillometer) was sampled over 0.5 metre interval s. Sampling is undertaken on site by splitting the core

in half, with one half submitted for analysis and t he other half retained in the core box for future r eference.

Uranium chemical assays are performed by the Saskat chewan Research Council (“SRC”) Geoanalytical

Laboratories located in Saskatoon. Sample preparati on involves crushing and pulverizing core samples t o

90% passing -106 microns. Splits of the resultant p ulps are initially submitted for multi-element ICP- MS

analysis following partial (HNO 3:HCl) and total (HF:HNO 3:HClO 4) digestions. Samples with ≥ 1,000 ppm U

(partial digest) are re-assayed for U 3O8 using an ISO/IEC 17025:2005 accredited method for the

determination of U 3O8 weight %. Pulp splits are digested using aqua-regi a and the solution analyzed for

U3O8 weight % using ICP-OES. In addition to internal ch ecks by SRC Geoanalytical Laboratories, the

Company has rigorous quality assurance and quality control ("QAQC") procedures including the insertion

of standard reference materials, blanks and field d uplicates. The assay data is subject to verificatio n

procedures by qualified persons employed by Denison prior to disclosure. For further details on the assay,

QAQC and data verification procedures please see De nison's Annual Information Form dated March 27,

2018 filed under the Company's profile on SEDAR (www.sedar.com).

Qualified Persons

Dale Verran, MSc, P.Geo, Pr.Sci.Nat., Denison's Vice President, Exploration, who is a Qualified Person in

accordance with the requirements of NI 43-101 has r eviewed and approved the technical information

contained in this release.

About Wheeler River

Wheeler River is the largest undeveloped high-grade uranium project in the infrastructure rich eastern

portion of the Athabasca Basin region, in northern Saskatchewan – including combined Indicated Mineral

Resources of 132.1 million pounds U3O8 at an average grade of 3.3% U3O8, plus combined Inferred Mineral

Resources of 3.0 million pounds U 3O8 at an average grade of 1.7% U 3O8. The project is host to the high-

grade Gryphon and Phoenix uranium deposits (discove red by Denison in 2014 and 2008, respectively),

and is a joint venture between Denison (63.3% and operator), Cameco Corp. (“Cameco”) (26.7%), and JCU

(Canada) Exploration Company Limited (“JCU”) (10%).

A Pre-Feasibility Study (“PFS”) was initiated for the Wheeler River project in Q3’2016 and is expected to

be completed during 2018. Prior to initiation of th e PFS, a Preliminary Economic Assessment (“PEA”) was

completed in 2016, which considered the potential economic merit of co-developing the high-grade Gryphon

and Phoenix deposits as a single underground mining operation. The PEA returned a base case pre-tax

Internal Rate of Return ("IRR") of 20.4% based on t he then current long term contract price of uranium

(US$44.00 per pound U 3O8), and Denison's share of estimated initial capital expenditures ("CAPEX") of

CAD$336M (CAD$560M on 100% basis).

The PEA is preliminary in nature and includes infer red mineral resources that are considered too

speculative geologically to have the economic considerations applied to them to be categorized as mineral

reserves, and there is no certainty that the prelim inary economic assessment will be realized. Mineral

resources are not mineral reserves and do not have demonstrated economic viability.

In January, 2017, Denison entered into an agreement with its Wheeler River Joint Venture partners,

Cameco and JCU, to fund 75% of Joint Venture expens es in 2017 and 2018 (ordinarily 60%) in exchange

for an increase in Denison's interest in the projec t to up to approximately 66%. Under the terms of th e

agreement, Cameco will fund 50% of its ordinary 30% share in 2017 and 2018, and JCU is expected to

continue to fund its 10% interest in the project. P ursuant to the agreement, as at December 31, 2017,

Denison had increased its interest in the Wheeler River project from 60% to 63.3%.

Further details regarding the Wheeler River project are provided in the NI 43-101 Technical Report for the

Wheeler River project titled “Technical Report with an Updated Resource Estimate for the Wheeler River

Property, Northern Saskatchewan, Canada" dated March 15, 2018 with an effective date of March 9, 2018.

A copy of this report is available on Denison’s website and under its profile on SEDAR at www.sedar.co m

and on EDGAR at www.sec.gov/edgar.shtml.

About Denison

Denison is a uranium exploration and development company with interests focused in the Athabasca Basin

region of northern Saskatchewan, Canada. In additio n to its 63.3% owned Wheeler River project, which

ranks as the largest undeveloped high-grade uranium project in the infrastructure rich eastern portion of

the Athabasca Basin region, Denison's Athabasca Basin exploration portfolio consists of numerous projects

covering approximately 353,000 hectares. Denison's interests in Athabasca Basin also include a 22.5%

ownership interest in the McClean Lake joint ventur e (“MLJV”), which includes several uranium deposits

and the McClean Lake uranium mill, which is current ly processing ore from the Cigar Lake mine under a

toll milling agreement, plus a 25.17% interest in the Midwest and Midwest A deposits, and a 65.45% interest

in the J Zone deposit and Huskie discovery on the W aterbury Lake property. Each of Midwest, Midwest A,

J Zone and Huskie are located within 20 kilometres of the McClean Lake mill.

Denison is also engaged in mine decommissioning and environmental services through its Denison

Environmental Services division and is the manager of Uranium Participation Corp., a publicly traded

company which invests in uranium oxide and uranium hexafluoride.

For more information, please contact

David Cates (416) 979-1991 ext. 362

President and Chief Executive Officer

Sophia Shane (604) 689-7842

Investor Relations

Follow Denison on Twitter @DenisonMinesCo

Cautionary Statement Regarding Forward-Looking 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 an d similar Canadian legislation concerning the busin ess, operations and financial

performance and condition of Denison. Generally, th ese forward-looking statements can be identified by the use of forward-looking

terminology such as "plans", "expects", "budget", " scheduled", "estimates", "forecasts", "intends", "anticipates", or "believes", or the

negatives and/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". In particular, this press release c ontains forward-looking information

pertaining to the following: exploration (including drilling) and evaluation activities, plans and objectives; potential mineralization of drill

targets and identified trends; estimates of Denison's mineral resources and the results of its PEA; plans and objectives with respect to

preparing a PFS to assess on a preliminary basis the potential for mine development an whether to proceed with a detailed feasibility

study; and Denison’s percentage interest in its properties and its plans and agreements with its joint venture partners, as applicable.

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.

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 forward-looking statements. Factors, such as

environmental impacts, stakeholder approvals, and capital needs can significant alter plans and achievements. 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 accurate and may differ materially from those anticipated in this forward looking information. For a discussion in respect of risks and

other factors that could influence forward-looking events, please refer to the factors discussed in Denison's Annual Information Form dated

March 27, 2018 under the heading "Risk Factors". These factors are not, and should not be construed as being exhaustive. Accordingly,

readers should not place undue reliance on forward-looking statements.

The forward-looking information contained in this press release is expressly qualified by this cautionary statement. Any forward-looking

information and the assumptions made with respect thereto speaks only as of the date of this press release. 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 Mineral Resources: This

press release may use the terms “measured”, “indicated” and “inferred” mineral 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.

Figure 1: Wheeler River basement geology and summer 2018 regional target areas.

Figure 2: Winter 2018 drill hole locations and assay highlights near Gryphon and along the K-North and K-West trends.

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