Forty-two pediatric patients were treated with ceftazidime ( CAZ ) in the doses ranging from 45.6 to 120 mg/kg/day for 2 to 10 days, and the clinical efficacy and side effects were evaluated. Among the 37 children with bacterial infections including pneumonia, bronchitis, tonsillitis, croup, cervical lymphadenitis, abdominal abscess and urinary tract infections, the results were excellent in 22, good in 12, fair in 2, and poor in 1 patient with pneumonia. Out of the 42 patients, 5 cases showed eosinophilia, but no clinical sign such as rash, fever or diarrhea, attributable to CAZ was observed during the study. The serum concentrations of CAZ in 4 patients ranged from 60.8 to 71.0 micrograms/ml (mean 66.1 micrograms/ml) at 30 minutes and from 0.5 to 1.2 micrograms/ml (mean 0.8 micrograms/ml) at 8 hours after 20 mg/kg intravenous bolus injection of the antibiotic. The mean serum half-life was 1.42 hours (85 minutes). Patients with impairment of renal function were excluded from this study.