PC-904 was administered to 16 pediatric patients and the following basic and clinical results were obtained. (1) PC-904 was administered 20 approximately 30 mg/kg. The serum peak level of PC-904 after drip intravenous infusion over 1 hour was 66.7 microgram/ml at 1 hour and T 1/2 of PC-904 was 67.8 minutes. PC-904 was administered 25 approximately 30 mg/kg intravenous one shot injection was 49.4 microgram/ml at 1 hour and T 1/2 of PC-904 was 52.2 minutes. (2) Urinary excretion rate was about 20% up to 6 hours after drip intravenous infusion of 20 mg/kg. In a case of intravenous one shot injection of 25 approximately 30 mg/kg, the excretion rate was 11.9 approximately 19.9%. (3) PC-904 was administered 60 approximately 120 mg/kg/day for 3 approximately 48 days to 5 cases of sepsis and bacterial endocarditis, 6 of pneumonia, 2 of sss syndrome (staphylococcal scald skin syndrome) and 3 of pyelonephritis. Clinical effects were excellent in 11 cases and good in 5 cases, effective ratio being 100%. (4) Pseudomonas aeruginosa, Staphylococcus epidermidis, Streptococcus viridans, Acinetobacter anitratus and Hemophilus influenzae isolated from clinical specimens disappeared by the treatment of PC-904, and Hemophilus influenzae isolated from clinical specimens disappeared by the treatment of PC-904. Escherichia coli and Klebsiella pneumoniae reduced. (5) As to the side effect by PC-904, s-GOT and s-GPT were elevated in 2 cases. Anemia, rash and fever were observed in each 1 case out of 16 patients though the causal relation with the agent was unknown.