Thirty children were treated with cefdinir (CFDN) for the evaluation of its clinical efficacy and side effects. Their ages ranged from 1 to 9 years. The dosage of CFDN ranged from 8.1 to 15.9 mg/kg/day with the treatment continued for 2 to 10 days. Twenty-eight of the 30 patients were evaluated for clinical efficacy; 10 patients with tonsillitis, 3 with scarlet fever, 4 with lower respiratory infections, 2 with otitis media, 2 with cervical lymphadenitis, 3 with urinary tract infections and 4 with skin and soft tissue infections. The remaining 2 patients who had viral diseases were included in the evaluation for side effects. Clinical responses were excellent in 14 patients, good in 12, fair in 1 and poor in 1 with an efficacy rate of 92.9%. Diarrhea was noted in one of the 30 patients. A pharmacokinetic study on CFDN was performed in 8 fasting patients whose ages ranged from 3 to 7 years. Serum concentrations of CFDN peaked at 0.59 to 1.76 micrograms/ml (mean 1.13 microgram/ml) at 2 hours after dosing of 3 mg/kg in 4 patients, and 0.89 to 2.49 micrograms/ml (mean 1.49 micrograms/ml) 2 or 3 hours after dosing of 6 mg/kg in the other 4 patients. The 8-hour urinary excretion rates were 16.0% to 21.3% (mean 17.4%) in 4 patients given a dose of 3 mg/kg and 10.9 to 21.1% (mean 15.5%) in 4 patients given a dose of 6 mg/kg.