The following studies were carried out in pediatric patients. 1. Serum levels of PC-904 were examined in 3 patients by 1 hour intravenous infusion of 20 mg/kg, reaching the peak of 22.5 approximately 25.5 microgram/ml at the end of infusion. Half life was 37 approximately 48 minutes. 2. Investigated in only 1 patient, the urinary excretion rate was 12.9% (0 approximately 6 hours). 3. The effect of PC-904 on blood pressure was examined in 1 patient, and no effect was observed. 4. Clinical effects of PC-904 were examined in 9 patients; urinary tract infection (6 cases) and Salmonella enteritis (3 cases). The daily dose was 32.6 approximately 93.0 mg/kg. The overall clinical effectiveness was 66.7%. As to causative organisms E. coli, Klebsiella and Salmonella were isolated. The clinical effects by the organisms were 100%, 0%, and 66.7%, respectively. 5. Slight elevation of GOT and GPT and eosinophilia were observed in each one case but these abnormalities rapidly returned to pre-treatment levels when the administration was discontinued. No other side effects were noticed.