Denver, CO. - Augusta Resource Corporation (“Augusta" or the “Company”) is pleased to announce that it has positive results from metallurgical test work that will impact production and process techniques to be used at the Company’s Rosemont copper/ molybdenum project located near Tucson Arizona. The new findings, as detailed below, will have a major positive impact on flow sheet design and the financial performance of the Rosemont project.

In summary Augusta has made the following determinations:

1)The Company is studying the feasibility of an open pit mine, concentrator and leaching facility with a concentrator production capacity of approximately 68,000 tonnes per day in order to produce estimated annual sales of 225 to 230 million pounds of recovered copper and over 5 million pounds of molybdenum over a 17-22 year period. Initial open pit optimization work indicates an overall waste to ore stripping ratio of approximately 1.55:1 may be obtainable depending on the outcome of geotechnical drilling and ultimate mine design layouts. The Company has not yet completed a full feasibility study. Therefore there is no certainty that economic operations will be realized until a positive study is completed.

2)Fractional analysis and flotation test work indicate that copper minerals are easily liberated and that copper sulfide recoveries of greater than 90% and concentrate copper grades in excess of 38% Cu are obtainable from a simple open cycle flotation flow sheet.

3)Test work indicates that the sulfide copper concentrate is amenable to hydrometallurgical techniques for the production of copper cathode on site. Flow sheets are currently being assessed.

4)Augusta has identified that initial material classified as overburden/waste contains soluble oxide copper as well as leachable sulfide copper at potentially economic grades. Augusta is currently conducting a work program (see March 17 press release) to quantify a NI 43-101 compliant oxide resource in the near surface zones of the deposit.

5)Past records and current drill assays show a significant content of bi-product silver and gold in addition to the recoverable molybdenum. Augusta is currently re-assaying drill core (see March 17 press release) to establish a silver resource.

Mountain States Research and Development (“MSRDI”) of Tucson Arizona, has recently completed metallurgical testing of representative composite samples in the main copper mineralized zones of the deposit. It was established that the predominant copper sulfide minerals are bornite, chalcocite and much lesser amounts of chalcopyrite than previously thought from the historic limited metallurgical work conducted by Anamax.

The predominance of bornite mineralization leads to new opportunities for producing much higher grade concentrates, opportunities to simplify the concentrator flow sheet, efficiently process mill concentrates using existing hydrometallurgical technologies, and to ultimately produce copper cathode on site.

In addition to the above findings, Augusta has also identified the potential for processing copper oxide mineralization. Column leaching tests conducted at MSRDI on oxide copper material from overburden samples combined with the Company’s current program of assaying and re-logging of existing historic drill core at Rosemont will allow for the determination ofthe grades and

distribution of economically recoverable copper within the low grade overburden. Only 30% of the diamond drill core penetrating overburden zones were assayed for oxide copper historically. Augusta is currently assaying oxide zone historic core. Initial on column leach test work indicate economic copper recoveries and acid consumption rates.

The metallurgical test work underway will also determine the amounts of silver and gold that report as a byproduct of sulfide copper production. This is concurrent with the Company’s previously announced program of re-assay of sulfide drill core for precious metals in order to establish an NI 43-101 compliant resource for silver and potentially for gold.

Test work is also underway to evaluate the application of water conservation measures commonly used in arid areas of Australia and South America; these conservation measures have the potential to reduce water evaporative losses as well as seepage losses of process water. Besides the environmental/conservation benefits, they could ultimately reduce operating costs over conventional tailings ponds in the arid climate of Arizona.

These positive evaluations affect the existing overall plant design, plant facility siting, utility demand, and project financial analysis. Augusta was scheduled to complete a pre-feasibility study during the first quarter 2006, but as a result of these new developments, the Company has decided to complete the pre-feasibility study in two stages in order to accommodate the new findings: 1) a preliminary economic assessment to be published late May 2006, and 2) the more comprehensive pre-feasibility study to be completed early in the third quarter 2006.

The schedule for completion of a full feasibility study early in the first quarter of 2007 remains unchanged. The Company’s 2006 twenty thousand (20,000) meter exploration, in-fill and geotechnical drilling campaigns at Rosemont are underway with three drill rigs in operation.

Qualified Persons

Augusta Resource Corporation has retained WLR Consulting, Inc. (WLRC) of Lakewood, Colorado to estimate the Rosemont Project mineral resources and develop mine designs as a part of a pre-feasibility mining study that is presently in progress. The mineral resource estimation work and preliminary mine design work was performed by or under the direction of Mr. William L. Rose, P.E., WLRC’s Principal Mining Engineer and an independent Qualified Person under the standards set forth by Canadian National Instrument 43-101. The metallurgical test work was performed by MSRDI under the supervision of Dr. Roshan Bhappu, P.E. an independent Qualified Person under the standards set forth by Canadian National Instrument 43-101. Augusta Resource Corporation has retained Washington Group International Inc., an integrated engineering, construction and management solutions company headquartered in Boise Idaho, as the primary author of the pre-feasibility study. Washington Group’s work is conducted under the review of Mr. John Ajie, P.E., an independent Qualified Person under the standards set forth by Canadian National Instrument 43-101.

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’s plans at its Rosemont 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 difficulties with 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 adequate financing on a 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. Should one 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, readers are advised 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 copper and exchange rates, 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.