June 8th, 2012 - Winnipeg, MB - Mainstream Minerals Corporation (TSX-V: MJO) ("Mainstream") is pleased to announce that it has closed the first tranche of a non-brokered private placement that was initially announced on May 22nd, 2012.  A total of 5,900,000 Units (as described below) were sold to subscribers resident in the Province of Ontario at a purchase price of $0.05 per Unit for gross proceeds of $295,000.00.  Mainstream intends to close the second and final tranche of this non-brokered private placement on or before June 29th, 2012.

Each Unit was comprised of one common share of Mainstream (a "Common Share") and one half (1/2) of one Common Share purchase warrant (each whole warrant a "Warrant"). Each whole Warrant may be exercised to purchase one Common Share upon payment $0.10 for a period of 12 months following the date of issuance. A finder's fee equal to     6 % of the subscription proceeds was paid to registered dealers for services rendered in introducing certain subscribers to the offering (each, a "Finder").  In addition to the finder's fee, brokers warrants equivalent to 6% of the number of Units subscribed for in this non-brokered placement were paid to Finders. Each broker warrant can be exercised to purchase one non-flow-through common share upon payment of $0.10 for a period of 12 months following the date of issuance.

The closing of this non-brokered private placement is subject to the approval of the TSX Venture Exchange Inc. The shares issued in connection with this non-brokered private placement will be subject to a four-month plus one-day hold period.

Mainstream Minerals intends to utilize the proceeds from the subscription for Units for working capital, general corporate purposes and for the maintenance of its mineral property claims.

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 possibly bringing such properties to commercial production. With a portfolio of six projects located in the Birch-Uchi Greenstone Belt, Red Lake Mining District, the company is well positioned to take advantage of the resurgence of exploration and development activities in this prospective belt located 80 kilometres due east of the main Red Lake Greenstone Belt. These six projects cover an area of approximately 28,600 acres and host several known gold occurrences and past producing mines. Other projects include the recently optioned Rowan Lake Project on the Cameron Lake-Pipestone Fault in the Kenora Mining District, the West Keefer Claims located in the West Timmins area in north-central Ontario and the Casa Berardi Claims in northern Québec.

MJO Shares Outstanding: 62,302,130

ON BEHALF OF THE BOARD

Signed "Michael Romanik"
Michael Romanik, President & CEO
(204) 222-0137
info@mainstreamminerals.com
www.mainstreamminerals.com

This news release includes certain forward-looking statements concerning the future performance of Mainstream Mineral Corporation's business, its operations and its financial performance and condition, as well as management's objectives, strategies, beliefs and intentions. The Company does not intend, and does not assume any obligation, to update these forward-looking statements. Forward-looking statements are frequently identified by such words as "may", "plan", "expect", "anticipate", "estimate", "intend" and similar words referring to future events and results. These forward-looking statements represent management's best judgment based on current facts and assumptions that management considers reasonable. The Company makes no representation that reasonable business people in possession of the same information would reach the same conclusions. All forward-looking information is inherently uncertain and subject to a variety of assumptions, risks and uncertainties, including the speculative nature of mineral exploration and development, fluctuating commodity prices, competitive risks and the availability of financing and as described in more detail in the Company's recent securities filings available at www.sedar.com. Actual events or results may differ materially from those projected in the forward looking-statements and readers are cautioned against placing undue reliance thereon.

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