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23. Highmark
2007 revenue: $12.4 billion
Fiscal year end: Dec. 31
2007 Employees: 18,500
Industry: Health care: Insurance
CEO: Kenneth R. Melani
Location: Pittsburgh, Pa.

Highmark provides health insurance to 4.6 million people in Pennsylvania through joint operating agreements with Blue Cross of Northeastern Pennsylvania and Independence Blue Shield.

NEXT: JM Family Enterprises

Last updated May 28 2008: 12:40 PM ET