An epidemiologic investigation was carried out in Ogaki Municipal Hospital to clarify the status of nosocomial MRSA Infection between 1989 and 1991. In 1989, coagulase type IV, enterotoxin A-producing, and phage group I strains, which were highly resistant to multiple antibiotics and isolated in the internal wards, accounted for 43.4% of all MRSA strains clinically isolated in the entire hospital. In 1990, coagulase type II strains that were sensitive to GM but resistant to FMOX and IPM increased. There were significant differences in the frequency of detection of various strains among wards, suggesting an inter-ward variation in MRSA strains. Changes in environmental strains reflected those in clinical strains. The findings suggest the necessity of measures not only for long-hospitalized MRSA carriers themselves but also for the environment of patients, medical staff, and those taking care of patients.