BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is the major pathogen of nosocomial infections. There are many reports that MRSA nasal cariers play a major role in the transmission of MRSA. We studied to assess the nasal carriage rates, therapeutic effects of nasal carriers and control of MRSA outbreak in a tertiary, acute and educational hospital. METHODS: From 1990 to 1997, eight MRSA epidemics were detected and investigated for outbreak control. We surveyed the MRSA colonization of anterior nares and hands of health care workers (HCW). MRSA was identified by staphylococcal broth, mannitol-salt- agar, Muller-Hinton-oxacillin agar. To identify the permanent carriers in the HCWs, the nasal swab was done weekly for 3 weeks. Two percent povidone iodine ointment or 2% mupirocin ointment was applied topically to treat the permanent MRSA nasal carriers. RESULTS: Of eight MRSA outbreaks, five epidemics occurred in the intensive care unit, all of them occurred in surgical departments and five of them occurred in winter seasons. For eight MRSA outbreaks, 351 HCWs were surveyed. The rates of transient carriers was 10.8% (38/351) and the rates of that were 9.0% (10/111) in medical doctors (MD), 12.5% (24/192) in registered nurses (RN) and 11.4% (4/35) in aid nurses (P=0.470). The rate of permanent carrier in doctors was 1.8%, and that in RNs was 3.7% (P=0.490). After topical therapy with 2% povidone iodine ointment or 2% mupirocin ointment for permanent carriers, MRSA was not identified for 2 months follow up. CONCLUSION: In MRSA epidemics, the rate of the transient carrier rate of MRSA in HCWs was 10.8% and the rate of the permanent carrier was 2.6%. The difference of carrier rates in HCWs was not significant statistically. The therapy for the permanent nasal carriers in HCWs with two percent povidone iodine ointment or 2% mupirocin ointment was very effective. And MRSA outbreaks were ended and controlled for 6months follow up.