Sultamicillin fine granules were used orally in 18 pediatric patients with infections in doses ranging 7.3-10.0 mg/kg t.i.d. or q.i.d. The following is a summary of the results: 1. Clinical efficacies in 16 cases with tonsillitis were excellent in 13 cases, good in 2 cases and fair in 1 case. Efficacy in 1 case of bronchitis and 1 case of pneumonia were good. The overall efficacy rate in the 18 cases was 94.4%. 2. Four out of 5 strains of Staphylococcus aureus were eradicated but 1 strain persisted. Three out of 7 strains of Haemophilus influenzae were rated as eradicated, 1 strain as decreased and 3 strains as persisted. Two strains of Streptococcus pyogenes and 3 strains of Haemophilus parainfluenzae were eradicated. The bacteriological efficacy rate for the 17 strains was 70.6%. Four strains out of the 17 were found to produce beta-lactamase and 3 strains were suspected, to produce the enzyme, but of these 7 strains, 5 strains were eradicated. 3. Diarrhea and loose stool were observed as side effects in each of 2 cases. It appeared that diarrhea was related to this drug. A slight elevation of GOT was observed in 1 case in laboratory tests. 4. This drug appears to be easy for children to take in terms of taste and smell.