UnitedHealth Group Signs Definitive Agreement to Acquire Sierra Health Services, Inc.

* Sierra Strengthens UnitedHealth Group Position in Fast-Growing Southwest Region

* Combination Broadens Senior Health Capabilities in Attractive Region for Retirees

* Brings Data Assets and Technology Resources that Support and Advance

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* UnitedHealth Group Reaffirms Plans for $4.0 Billion to $4.5 Billion Share Repurchase in 2007

MINNEAPOLIS & LAS VEGAS -- UnitedHealth Group (NYSE:UNH) and Sierra Health Services, Inc. (NYSE:SIE) (Sierra) today announced that they have signed a definitive merger agreement under which UnitedHealth Group will acquire all of the outstanding shares of Sierra, a diversified health care services company based in Las Vegas, for $43.50 per share in cash, representing a total equity value of $2.6 billion. The transaction, which has been approved by the Boards of Directors of both companies and is expected to close by the end of 2007 or sooner, is subject to state and federal regulatory approvals, including in Nevada, California and Texas, approval by Sierra's stockholders, and other customary conditions.

"We have completed extensive due diligence, and expect Sierra's positive performance to continue," said Mike Mikan, chief financial officer of UnitedHealth Group. "Sierra is a financially strong organization with very stable operations and systems, and has a long and well-recognized history of consistently and profitably delivering high-quality, affordable health care in Nevada."

Sierra is a leading provider of health benefits and services, serving approximately 310,000 employer-sponsored health plan members in Nevada and 320,000 people in senior and government programs throughout the United States. The combined business in the Nevada region will continue under the leadership of Sierra's chairman and chief executive officer Anthony M. Marlon, M.D. and his management team. The transaction combines Sierra's broad local networks of high-quality health care providers and services with UnitedHealth Group's organized system of care providers and clinical centers of excellence programs throughout the United States, its significant capabilities and technologies to support consumers, and its leadership role in making the health care system work better for all constituents.

UnitedHealth Group president and chief executive officer Stephen J. Hemsley said, "Combining UnitedHealthcare and Sierra brings together two strong and innovative companies that each have a heritage of providing consumers access to affordable, quality medical care. The combined enterprise will have the scale, resources and commitment to offer the most comprehensive range of affordable services to our clients in the Southwest, as well as for clients with business interests across the country.