(Un-levered economics run at $1.20/lb Copper (“Cu”), $10/lb Molybdenum (“Mo”) and $7.50/oz Silver (“Ag”) see PA report features below for study assumptions and summary.)

Case 1 assumes a conventional open pit mine, concentrator producing a copper sulphide concentrate, a molybdenum concentrate (“MoS2”), and with silver as a by-product credit contained in the copper concentrate. The copper concentrate is planned to be shipped to smelters in the US southwest or Mexico.

Case 2 adds production from the leaching of existing oxide copper resources (approximately 60 million tons) and evaluates the addition of a concentrate leach circuit and a solvent extraction/electrowinning (“SX/EW”) plant designed to produce LME grade copper cathode. This Case assumes production of LME grade cathode

Case 1 (Concentrate production only)

• Trailing Case Prices, as of 5/31/06:

o Cu - average of 3 years trailing LME cash official prices

oMo - average of 3 years trailing price data for molybdenum oxide, F.O.B. North America.

oAg – constant $7.50/oz

•Forward Case Prices, as of 5/31/06:

oCu - average of the LME 27 month official forward price and 3 years of trailing LME official

cash prices.

o Mo – same as Trailing Case Prices o Ag – same as Trailing Case Prices

Case 2 (Cathode and Concentrate production)

•Trailing Case Prices: Same as Base Case

•Forward Case Prices: Same as Base Case

Environmental

Five fundamental characteristics set the Rosemont Project operating plans apart from other copper mines in the area: isolated location, project size, sustainable water supply, water conservation, and dry tailings disposal. The proposed mining facilities are located entirely within the Barrel Basin, with the pit located on private lands within this isolated drainage. The land requirements for the Rosemont project will total less than 4,000 acres, which is less than a third of the 13,272 acres of public land sought by earlier mining companies. Water conservation programs use the best available modern technology to reduce water needs to

less than a third of other large copper mines in the area. Dry tailings management technologies will conserve water as well as eliminate the need for construction of a large conventional tailings impoundment. These five characteristics of the Rosemont project are expected to facilitate the permit review and approval process.

In addition, Augusta proposes to utilize concurrent reclamation with construction and re-vegetation of perimeter berms along the outside of the waste rock storage areas, within the first few years of mine operation. Augusta has used viewshed analyses in the planning process to optimize locations and profiles of facilities for minimal visual impact.

Incorporating best available demonstrated control technologies, concurrent reclamation, and utilizing a sustainable water supply; the Company is scheduled to initiate the formal permit application and review process for the proposed low profile mine during July 2006.

Mining & Production

The mining process at Rosemont will be a conventional modern hard rock open pit operation. The open pit mine, concentrator and leaching facility will include a nominal concentrator production capacity estimated at 75,000 tons per day. The proposed Rosemont mine is expected to annually produce 226 to 233 million pounds of recovered copper, approximately 5.1 million pounds of recovered molybdenum and approximately 6.7 million ounces of recovered silver as a by-product credit over the mine life.

Infrastructure

The Rosemont project is located in Pima County, approximately 50-km southeast of Tucson, Arizona accessible by Highway 83. There are two available power lines located within 10 miles and rail within 15 miles. The city of Tucson has an experienced workforce for mining as four large open pit copper mines have operated for decades within 25 miles of Rosemont. All infrastructure capital and operating costs are included in the economic analysis.

Capital Costs

Direct capital costs (“CAPEX”) for the project are estimated at $636M for Case 1 and $806M for Case 2. CAPEX estimates include all infrastructure, mine and concentrator costs, as well as a capital contingency totaling $83M (Case 1) and $105M (Case 2). The additional costs in Case 2 include production of cathode copper oxide heap leach from lined pads and also includes a copper concentrate leach circuit allowing for approximately 75% of the copper contained in the sulphide concentrate to report in solution to an SX/EW plant on site that would be designed to handle a blend of solutions from the oxide leach pads and the concentrate leach circuit. There was a 15% contingency provision included in the capital estimate.

Operating Costs

The PA results indicate that the Rosemont deposit may be a very low cost copper producer. The pretax cash costs are estimated to be $0.42/lb of copper produced under Case 1, and $0.37/lb for Case 2. Operating costs in Case 2 include acid costs, leach pad operation and the costs associated with concentrate leaching and running the SX/EW plant.

Next Steps

The PA marks the beginning of the detailed development process for mining and production operations at Rosemont. The Company is embarking on a final Feasibility Study scheduled for completion early in 2007. In March 2006, the Company commenced a 20,000-meter exploration, in-fill and geotechnical drilling campaign on the Rosemont deposit with five drill rigs currently in operation. A NI 43-101 Technical Report on PA results has been filed under the Company’s profile on SEDAR at www.sedar.com, as well as at www.augustaresource.com.

The PA has been completed following one year of current exploration by the Company at the Rosemont Property, and should be read in conjunction with the NI 43-101 compliant Mineral Resource Estimate and Technical Report for the Rosemont Deposit dated April 21, 2006, which was completed by WLR Consulting, Inc. (see news release dated January 24, 2006), and accessible on the Company’s website at www.augustaresource.com or on SEDAR at www.sedar.com. The PA is based on NI 43-101 Mineral Resource Estimate of 6.4 billion lbs of Cu equivalent (442,000,000 tons at 0.73% Cu equivalent) in measured and indicated resources and 1.9 billion lbs of Cu equivalent (145,000,000 tons at 0.67% Cu equivalent) in inferred resources. Please refer to the Company’s January 24, 2006, news release which provides supporting information for equivalence. The PA is preliminary in nature and includes the use of inferred resources that are considered too speculative geologically to have economic considerations applied to them that would enable them to be categorized as mineral reserves. Thus, there is no certainty that the preliminary assessment will be realized.

The PA was prepared by an integrated engineering team that included Washington Group InternationalInc.,WLR Consulting Inc., and Augusta personnel. Washington Group International Inc., an integrated engineering, construction and management company headquartered in Boise, Idaho, was retained as the primary author of the preliminary assessment study. The PA was conducted under the overall review of Mr. John Ajie, P.E., of Washington Group International Inc., an independent Qualified Person under the standardssetforthbyNI43-101.

ABOUT AUGUSTA RESOURCE CORPORATION - Augusta Resource Corp. is a mineral exploration and development company responsibly advancing copper and other base metal assets in the U.S. southwest. The Company’s Rosemont Property is located in Pima County, approximately 50 km southeast of Tucson, Arizona, and contains four known potentially open-pit copper/molybdenum deposits. The Rosemont deposit contain 6.4 billion lbs of Cu equivalent (442,000,000 tons at 0.73% Cu equivalent) in measured and indicated resources and 1.9 billion lbs of Cu equivalent (145,000,000 tons at 0.67% Cu equivalent) in inferred resources. Please refer to the Company’s news release dated January 24, 2006 for further details. Augusta has additional exploration properties in Nevada. The Company is traded on the Canadian TSX Venture Exchange under the symbol ARS.

For additional information please visit www.augustaresource.com or contact:

ON BEHALF OF THE BOARD OF DIRECTORS

“Gil Clausen”

_________________________

Gil Clausen

President and CEO

SPECIAL NOTICE REGARDING FORWARD-LOOKING STATEMENTS

Certain of the statements made and information contained herein and in the documents incorporated by reference may contain “forward-looking statements” including statements concerning the Company’splansatitsRosemont Property, and other mineral properties, which involve known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of the Company, or industry results, to be materially different from any future results, performance or achievements expressed or implied by such forward- looking statements. Forward-looking statements are subject to a variety of risks and uncertainties which could cause actual events or results to differ from those reflected in the forward-looking statements, including, without limitation, risks and uncertainties relating to the interpretation of drill results and the estimation of mineral resources and reserves, the geology, grade and continuity of mineral deposits, the possibility that future exploration, development or mining results will not be consistent with the Company’s expectations, metal recoveries, accidents, equipment breakdowns, title matters, labor disputes or other unanticipated difficultieswith or interruptions in production, the potential for delays in exploration or development activities or the completion of feasibility studies, the inherent uncertainty of production and cost estimates and the potential for unexpected costs and expenses, commodity price fluctuations, currency fluctuations, failure to obtain adequatefinancingona timely basis and other risks and uncertainties, including those described under Risk Factors Relating to the Company’s Business in the Annual Information Form and the management’s discussion and analysis.Shouldone or more of these risks and uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those described in forward-looking statements. Accordingly,readersareadvised not to place undue reliance on forward-looking statements. Forward- looking statements include statements regarding the expectations and beliefs of management, the assumed long-term price of copperandexchangerates, the estimation of mineral reserves and resources, the realization of mineral reserve estimates in future expected production, anticipated future capital and operating costs, and the potential of the Company’s properties and expectations of growth. Except as required under applicable securities legislation, the Company undertakes no obligation to publicly update or revise forward-looking statements, whether as a result of new information,future events or otherwise.