According to the serological grouping of temperate phages isolated from clinical isolates, many strains of them were a doubly lysogenic strain carring serotype A and B. Staphylococcus aureus MS3878 was also a doubly lysogenic strain carring serotype A and B. Phages induced from Staphylococcus aureus MS3878 were purified followed by density gradient centrifugation in CsCl, and these phages were used for transduction analysis. The transduction frequency of the nonconjugative drug resistance plasmids rms6 and rms7 with phage serotype A was about 10 ^-10, but that with phage serotype B was 10 -5 to 10 ^-7.