1. Cefuroxime (CXM) was studied for absorption and excretion in 4 pediatric patients given one shot intravenous injection of 20 approximately 25 mg/kg. The following serum levels were determined: 24.5 approximately 38.0 micrograms/ml at 30 minutes (mean 33.3 +/- 6.1 micrograms/ml), 10.0 approximately 17.0 micrograms/ml at 1 hours (mean 13.9 +/- 3.3 micrograms/ml), 3.4 approximately 7.6 micrograms/ml at 2 hours (mean 5.2 +/- 1.9 micrograms/ml, 0.7 approximately 2.1 micrograms/ml at 4 hours (mean 1.3 +/- 0.6 micrograms/ml, 0.1 approximately 0.3 microgram/ml at 6 hours (mean 0.2 +/- 0.1 microgram microgram/ml). Half-life (T 1/2) was 0.65 approximately 0.88 hour (mean 0.75 +/- 0.10 hour). Urinary levels were 1,280 approximately 7,100 micrograms/ml at 0 approximately 2 hours, 96 approximately 3,400 micrograms/ml at 2 approximately 4 hours, 68 approximately 250 micrograms/ml at 4 approximately 6 hours. Urinary recovery rate at 0 approximately 6 hours was 54.1 approximately 74.4% (mean 61.8 +/- 9.4%). 2. From the study on spinal fluid concentration in pediatric patients with Haemophilus influenzae-induced meningitis, the dose of CXM 52.2 mg/kg was given to 1 pediatric case with this disease by one shot intravenous injection. Spinal fluid levels were presumed as 9.0 micrograms/ml at 30 minutes, 6.8 micrograms/ml at 1 hour, 3.8 micrograms/ml at 2 hours and 1.2 micrograms/ml at 4 hours. 3. CXM was studied in 19 pediatric patients with bacterial infection for clinical efficacy, bacteriological effect and side effect. Clinical result was found good in 1 with purulent meningitis; excellent in 9 out of 15 with acute lobar pneumonia or acute bronchopneumonia, and good in remaining 6 cases; good in 2 with acute bronchitis; excellent in 1 with acute pyelonephritis. This represents efficacy ("excellent" plus "good") rate of 100%. Of 5 strains of H. influenzae presumed as causative organisms, 4 were disappeared and 1 was reduced. Two strains of Streptococcus pneumoniae and 1 strain of Escherichia coli were disappeared. No side effect was noted in terms of clinical symptom. Laboratory examination showed elevation of GOT and GPT in 1 case, but these elevated values returned to normal after the end of the CXM treatment.