Express Scripts, Inc., an independent pharmacy benefit manager (PBM), provides integrated PBM services including network pharmacy claims processing, mail pharmacy services, benefit design consultation, drug utilization review and formulary management. The Company offers PBM services to clients in the United States and Canada. As of January 1, 2003, some of the Company's largest clients included United HealthCare Insurance Company, which manages the AARP Pharmacy Service, Blue Cross Blue Shield of Massachusetts, Blue Shield of California, Mutual of Omaha, the State of Georgia, Mid Atlantic Medical Services Inc., Group Health Incorporated, and effective, March 2003, the Department of Defense TRICARE Management Activity.