Seventeen newborn and young infants including 6 premature infants were treated with ceftazidime (CAZ) and the clinical efficacy and side effects were evaluated. Ages of the patients ranged from zero to 55 days, and their body weights ranged from 1.35 to 3.87 kg. Doses of CAZ ranged 10-50 mg/kg every 6 to 12 hours for 3 to 14 days. Twelve infants with infections including meningitis, sepsis, pneumonia and urinary tract infections, were considered to have responded to the CAZ treatment. Among them, results were excellent in 2, good in 9 and fair in 1 patient. The drug was well tolerated, but 1 had diarrhea and 3 patients had eosinophilia among the 17 patients. The pharmacokinetics of CAZ was studied in 22 patients including 11 premature infants. Their ages ranged from 1 to 60 days, and body weights ranged from 0.85 to 3.96 kg. Serum concentrations in 7 patients ranged from 24.2-38.5 micrograms/ml at 30 minutes after single doses of 10 mg/kg intravenous bolus injections and 4.36-12.4 micrograms/ml at 6 hours. Mean elimination half-lives of the drug were 3.20 hours in 2 patients under 7 days of age and 2.31 hours in 5 patients from 7 days of age or older. In 8 patients, serum concentrations ranged 32.6-57.9 micrograms/ml at 30 minutes and 8.10-20.7 micrograms/ml at 6 hours after single doses of 20 mg/kg. Elimination half-lives were 3.53 hours in 4 patients under 7 days of age and 2.79 hours in 4 patients from 7 days of age or older.(ABSTRACT TRUNCATED AT 250 WORDS)