Laboratory and clinical studies on cefpirome (CPR, HR 810), a newly developed cephem antibiotic, were performed. The results obtained are summarized as follows: 1. Absorption and elimination of the drug were examined in a total of 7 children including 3 cases of administered with 20 mg/kg intravenous bolus injection (i.v.), 2 cases with 20 mg/kg drip infusion (d.i.v.) for 60 minutes and 2 cases with 40 mg/kg (d.i.v.) for 60 minutes. Maximum serum levels were attained immediately after i.v. or d.i.v. Cmax's were 233 +/- 7.6, 88.5 +/- 14.5, and 116 +/- 15 micrograms/ml, respectively for the above 3 modes of administration. These values were determined using a bioassay method with Bacillus subtilis ATCC 6633. T 1/2 (beta)'s were 1.18 +/- 0.17, 1.61 +/- 0.28 and 2.68 +/- 0.83 hours, respectively. Cumulative urinary recovery rates were 40.2-69.8% in a period of 0-6 hours after admissions. 2. Clinical efficacies were evaluated in a total of 20 patients with ages ranging from 9 months to 11 years. The treated cases were 6 cases of acute pneumonia, 4 cases of acute bronchitis, 4 cases of acute purulent tonsillitis, 2 cases of acute urinary tract infections, 2 cases of cellulitis, 1 case of purulent lympadenitis and 1 case of acute otitis media. The clinical efficacy rate was 94.7%. Adverse reactions occurred in no patients. Abnormal changes in laboratory test values involved only 1 case with elevated GOT and GPT. CPR was considered to be a safe and useful drug in treating various infectious diseases in children.