Cefodizime (CDZM), a newly developed injectable cephem antibiotic, was given via bolus intravenous injection at each of 3 dose levels of 10, 20 and 40 mg/kg to each 3 children, and serum and urinary levels and urinary recovery rates were followed. A total of 57 patients received CDZM in the following regimen via bolus intravenous injection, and clinical efficacies, and microbial responses were evaluated. Mean dosage per application: 20.9 mg/kg, number of application per day: between 2 and 4 (2 times for 3 patients, 3 for 26 patients and 4 for 28 patients), mean duration of the therapy: 1 week. Patients consisted of 1 case of peritonsillar abscess, 2 acute bronchitis, 38 pneumonia, 8 urinary tract infection, 1 staphylococcal scalded skin syndrome, 2 cellulitis, 4 purulent lymphadenitis and 1 typhoid fever. In addition to the patients mentioned above 6 patients who dropped out were involved in the evaluation of adverse reactions and influence of the drug on laboratory test data, and the following results were obtained. 1. Five minutes after bolus intravenous injection in doses of 10, 20 and 40 mg/kg, serum levels determined by the bioassay method were at their maxima, i.e. 114.0, 264.6 and 461.6 micrograms/ml, respectively. Serum levels of drugs were dose-dependent throughout all the dosage levels tested. Mean serum half-lives of the drug were 1.757, 1.552 and 1.668 hours, respectively, for the 3 dose levels. Serum levels of the drug determined by the HPLC method were similar to those by the bioassay method: The maximum serum levels occurred at 5 minutes after administration, mean maximum concentrations were 105.5, 264.0 and 461.7 micrograms/ml for the 3 dose levels, and a dose response was noted for the 3 dose levels. The half-lives were 1.755, 1.598 and 1.668 hours, respectively. 2. Mean maximum concentrations in urine determined by bioassay for 2 of 3 cases received 10 mg/kg and 3 cases each given 20 and 40 mg/kg of CDZM were 884.3, 3,061 and 7,352 micrograms/ml, respectively, in the first 2 hours after administration. These levels were also dose-dependent. Mean recovery rates were 74.4, 78.4 and 71.5%, respectively, in the first 8 hours after administration. Mean maximum concentrations in urine measured by HPLC were similar to those determined by bioassay, i.e. 962.3, 3,404 and 7,899 micrograms/ml in the first 2 hours. They were, also, dose-dependent. Mean recovery rates were 82.1, 86.0 and 76.5%, respectively, in the first 8 hours after administration. The HPLC determinations gave slightly higher levels than the bioassay.(ABSTRACT TRUNCATED AT 400 WORDS)