S-1108 in a fine granular form was administered in 14 children and its safety and efficacy in bacterial infections were evaluated. Among them, 2 cases of cystitis and 1 case of pneumonia were considered unevaluable for the efficacy. The results obtained are summarized as follows. 1. The overall clinical efficacy rate was 81.8% in the eleven evaluable cases treated with S-1108 fine granules including 5 cases of pharyngitis, 2 cases each of tonsillitis, pertussis and cystitis. 2. Bacteriological efficacy of 100% was achieved against pathogens identified in 5 children including 1 case each of Staphylococcus aureus, Streptococcus pyogenes and Haemophilus influenzae and 2 cases of Escherichia coli. 3. The only abnormal laboratory test results observed were eosinophilia and leukocytopenia in one case each. Diarrhea was recorded in 1 case. Judging from the above results, it appears that S-1108 in the fine granular form is an effective, useful and safe antibiotic of first choice for the treatment of infections in the pediatric field.