Most methicillin-resistant Staphylococcus aureus (MRSA) isolates are multiply resistant to various antimicrobial agents. Therefore, MRSA strains have become a serious problem in the clinical setting. However, it should be noted that the frequency of isolation of strains resistant to aminoglycoside and minocycline was not significantly different between low- and high-MRSA isolates and the isolation frequency of high-MRSA strains, less susceptible to not only beta-lactam antibiotics but also to macrolide antibiotics and quinolones, was significantly higher than the corresponding values for low-MRSA strains. These results suggest that high-MRSA strains were selected by antimicrobial agents for the treatment with the patients.