Group Health Cooperative of Puget Sound is a consumer-governed health maintenance organization with approximately 380,000 enrollees. The enrollees are provided pharmacy services at 3 hospital locations, 28 primary care clinics, and 4 specialty care clinics. A Pharmacy and Therapeutics Committee (P&T) oversees cooperative-wide formulary management of all medications used for inpatients and outpatients, thus decreasing the stock of medications in all the pharmacy locations while providing representative drugs from all therapeutic classes. A subcommittee of the P&T committee, the Antibiotic Usage Review Group, manages the antimicrobial formulary. It consists of staff members from infectious disease, nursing, pulmonary medicine, family practice medicine, and pharmacy departments. The group provides recommendations based on seven specific areas; reviewing requests from prescribers for the addition of new antimicrobial agents to the formulary; evaluating antimicrobial agents by drug class; reviewing potential drugs for therapeutic interchange; developing use criteria for specific antimicrobial agents or classes; developing treatment algorithms for specific infectious diseases; performing drug use evaluations for antimicrobial agents; and approving the use of nonformulary antimicrobial agents. This approach has limited the inappropriate prescribing of antimicrobials and has increased the medical staff's knowledge on appropriate use of these agents.