We have carried out laboratory and clinical studies on norfloxacin (NFLX, AM-715). The results are summarized as follows. NFLX was given through oral administration to one child each at dose levels of 1.7 mg/kg, 2.4 mg/kg and 3.2 mg/kg. After administration, peak serum levels of NFLX obtained for the 3 dose levels were 0.16 micrograms/ml at 1 hour, 0.69 micrograms/ml at 2 hours, 0.81 micrograms/ml at 1 hour, respectively, and half-lives were 2.5 hours, 1.8 hours and 2.7 hours, respectively. NFLX was given through oral administration to 2 children at a dose level of 4.4 mg/kg and to another child at a dose level of 4.8 mg/kg. After administration, mean peak serum levels of NFLX obtained were 1.17 +/- 0.48 micrograms/ml and half-lives were 3.0 +/- 0.5 hours. Urinary excretion rates of NFLX were 14.5% and 28.4% in the first 8 hours after administration of 1.7 mg/kg and 3.2 mg/kg, respectively, and 29.1% in the first 6 hours after administration of 2.4 mg/kg. Mean urinary excretion rates of NFLX were 38.5 +/- 13.0% in the first 8 hours after administration of 4.4 mg/kg and 4.8 mg/kg. Treatment with NFLX was made in 33 cases of pediatric bacterial infections including 5 cases of tonsillitis, 14 cases of enteritis, 10 cases of UTI and 1 case each of bronchitis, balanoposthitis, impetigo and pustulosis. Results obtained were excellent in 14 cases, good in 15 cases. No significant side effect due to the drug was observed in any cases.