Fusidic acid (FA) resistance (MIC greater than or equal to 12.5) was found in only five of 123 strains of S. aureus isolated during the period from January, 1987, to March, 1988; the FA resistance rate soared up to 42 of 81 strains isolated during the period from April, 1988, to October, 1988. In contrast, all strains of S. aureus isolated in Kochi prefecture during the period from September, 1987, to September, 1988, were susceptible to FA. Our data clearly demonstrate an explosive increase of FA resistant S. aureus in Japan. However, regional differences currently exist in the emergence rate of FA resistant S. aureus.