Mainstream Minerals Drilling Alert: Bobjo Mine Project in Red Lake, ON

Mainstream Minerals Corporation (TSX.V: MJO) announces that it and its joint venture partner King's Bay Gold Corporation (TSX.V: KBG) are proceeding with a first phase $1 million diamond drill program on their high-grade gold Bobjo Mine project, Red Lake, Ontario.

(PRWEB) June 27, 2007 -- Mainstream Minerals has informed King's Bay Gold that two diamond drills are now on the Bobjo property and that drilling will commence immediately. This Bobjo project was the site of a high-grade gold discovery in December 2006, where surface grab sampling of one vein, with a width of up to approximately 6 metres returned ultra high-grade gold values of up to 2,942.7 g/t (85.84 oz/t) and 806.9 g/t (23.54 oz/t).

The joint venture is 50% Mainstream Minerals and 50% King's Bay Gold with Mainstream Minerals being the operator of the project. John Archibald, P. Geologist is the Qualified Person under National Instrument 43-101. All of the drilling samples will be analyzed by Accurassay Laboratories of Thunder Bay, Ontario, using the standard fire assay method.

The Bobjo Mine property is located between the former South Bay and Uchi Lake gold mines. It is comprised of a total of 9 patented and 86 unpatented claim units totaling 3,800 acres with a power transmission line passing through the southern part of the property. The area has a history of gold and base metal production dating back 80 years and the work presently being carried out by the partners represents the commencement of the first modern, systematic exploration of the property.

About Mainstream Minerals:

Mainstream Minerals Corporation is a mineral exploration and development company focused on precious metal mining properties with economic potential, with the aim of bringing such properties to commercial production. The Company's portfolio of properties is primarily located in northwestern Ontario's prolific Red Lake Gold Camp.

Subsequent to the closing of the IPO Offering as announced on June 12th, 2007, the Company has 12,816,224 common shares issued and outstanding and has cash resources on hand of approximately $1.6 million.

Mainstream Minerals Corporation:

Gerald Colborne

President & CEO

(204) 222-0137

www.mainstreamminerals.com

The TSX Venture Exchange has not reviewed and does not accept responsibility for the adequacy or accuracy of this release. Some of the statements contained in this release are forward-looking statements, such as estimates and statements that describe MJO's future plans, objectives or goals, including words to the effect that MJO or management expects a stated condition or result to occur. Since forward-looking statements address future events and conditions, by their very nature, they involve inherent risks and uncertainties.

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