Restriction endonuclease (Sma I) digestion patterns of chromosomal DNAs from 459 group B streptococci (GBS) isolated in two hospitals (C and S) in Toyama Prefecture were analysed by pulsed-field gel electrophoresis (PFGE). Results were summarized as follows. 1) One hundred thirty eight isolates of GBS serotype Ia, 174 of serotype III, 102 of serotype JM-9 and 45 of serotype NT-6 were further divided into 56, 41, 36 and 19 PFGE types, respectively. 2) Appreciable differences in the distribution of PFGE types were not observed between C and S hospital isolates, nor among specimens from which GBS strains were isolated. 3) Long-term inspection of 5 patients, from whom the same serotype strains were repeatedly isolated, revealed that some changes in PFGE types were observed in 2 patients, but not in the other 3.