Sustained control of endemic methicillin-resistant Staphylococcus aureus (MRSA) originating from multiple sources has not been reported. We describe a simple, inexpensive program based on feedback to physicians that resulted in significant reduction of nosocomial MRSA. When nosocomial cases were identified, the epidemiologist contacted the team resident to encourage increased emphasis on hand washing. Handouts, periodic hand cultures of house staff, and monthly presentations at morning report were also employed. In the first 15 months, nosocomial MRSA decreased from 1.025 to 0.508 cases per 1,000 patient days (p less than 0.01). Monthly rates were significantly decreased for 9 months of 1989 and the first 2 months of 1990. Feedback and assignment of responsibility resulted in a 50% reduction in nosocomial MRSA that has been sustained for 15 months.