Group B Streptococcus was isolated from the clinical materials of the patients examined in the Kobe Central Municipal Hospital, in 1974 to 1979. 1. Clinical isolates were all resistant to bacitracin. 2. Serotypes of 19 isolates were type III in 12 strains, Ia in 3, Ic in 2 and untypable in 2. 3. The MICs were determined to 15 antibiotics, and the results showed that penicillin G was the best and in the order of decreasing potency, cefotaxime, ampicillin, ceftizoxime and cefoperazone. 4. Compared with group A Streptococcus, the sensitivity of group B Streptococcus to penicillin G and ampicillin was inferior by 2 to 3 tubes. 5. Based on the above results, the significance of the cephalosporin antibiotic of the third generation, particularly cefotaxime, was evaluated in the treatment of infectious diseases of the newborn infants.