MICREX DEVELOPMENT CORP.

A mineral exploration and development company operating in Canada and the United States

TSX Venture Exchange symbol "MIX"
SEC 12 g (3) Exemption 82-4281

For immediate release

May 15, 2007

Bighorn Joint Venture Agreement

Micrex announced today that it has signed a Joint Venture Agreement on the northern British Columbia Bighorn Project with Mountain Rio Resources Inc., a private Company based in Edmonton.

Under this agreement Mountain Rio has purchased a one eighth (1/8th ) working interest in the Bighorn Project for $300,000. The previous Joint Venture Earn in Agreement announced in the May 9, 2006 Press Release has been superceded and retired in favour of this new Joint Venture Agreement.

Mountain Rio has demonstrated a willingness to finance and aggressively pursue projects of common interest with Micrex and the two companies believe that their combined expertise and common goals will benefit both companies.

Mountain Rio is currently working with Micrex on the Deadwood/Sunburst Project in New Mexico. They report that they have a geological crew on the ground preparing for this season’s exploration effort, which will focus on a drilling program at Deadwood and surface exploration of nearby claims staked by Micrex last year.

Further information may be obtained from Perry Meszaros or S.E. Marshall at (780) 448-0922
or email at mixinfo-1@mixcorp.com

Web site address: www.mixcorp.com

MICREX DEVELOPMENT CORP.

Peace River Diamond Property • Burmis Magnetite/Titanium Property • St. Charles de Bourget Magnetite/Titanium Property • Fort Steel Placer Property • Bighorn Gold Mine • Banks Gold Mine • Mount Royal Gold Mine • Deadwood Gold Mine • Sunburst Gold Property

THE TSX VENTURE EXCHANGE HAS NOT REVIEWED AND DOES NOT ACCEPT RESPONSIBILITY FOR THE ADEQUACY OR ACCURACY OF THIS RELEASE.

FORWARD LOOKING STATEMENTS

Certain statements in this news release are "forward-looking statements", which reflect management's expectations regarding its property and business operations. All statements other than statements of historical fact contained in this news release are forward-looking statements. Such forward-looking statements involve risks and uncertainties, as they reflect management's current beliefs and are based on information currently available to management. Actual results may differ materially from those anticipated in the statements made. The forward-looking statements are expressly qualified in their entirety by this cautionary statement. The forward-looking statements are made as of the date of this news release and Micrex assumes no obligation to update or revise them to reflect new events or circumstances except as expressly required by applicable securities law. Further information regarding the uncertainties and risks can be found in the disclosure documents filed by Micrex with the securities regulatory authorities, available at www.sedar.com.

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