Although increasing incidence of infections with methicillin-resistant Staphylococcus aureus (MRSA) has been reported in other countries, the situation of our country is not clearly ascertained. S. aureus isolated from various clinical specimens at Yonsei Medical Center was tested for the antimicrobial susceptibility by the Kirby-Bauer method. The MRSA isolated in 1981 was tested for the antimicrobial susceptibility by agar dilution method. Following results were obtained. 1) Increased prevalence of MRSA from 0% to 31.7% was noted during the period of August 1979 to June 1982. 2) MRSA was isolated only from inpatients but not from outpatients. No difference was noted in the isolation rate by sources of specimen. 3) Cephalothin was the most active drug against MRSA, showing the lowest MIC range, MIC50 and MIC90. Among the MRSA isolates, 91.2% was susceptible to this drug. 4) To amikacin, 58.8% of the MRSA was susceptible while all were resistant to dibekacin, gentamicin, tobramycin. It is concluded from this study that infections due to MRSA is increasing among inpatients, and increasing difficulty is anticipated to control MRSA infection as the amikacin is the only active aminoglycoside.