Sulbactam/cefoperazone (SBT/CPZ) was evaluated in the treatment of pediatric patients to have the following results: Peak serum concentrations which occurred just after the drip infusion of 20 mg/kg SBT/CPZ were 36.4 micrograms/ml and 8.6 micrograms/ml for CPZ and SBT, respectively. The half-life of CPZ was 1.91 hours, and that of SBT, 0.97 hour. Following the 40 mg/kg drip infusion, the peak serum concentration of CPZ was 79.1 micrograms/ml, and that of SBT, 27.0 micrograms/ml. The half-lives were 1.99 hours for CPZ, and 1.07 hours for SBT, respectively. In 6 hours after drip infusion of 20 mg/kg and 40 mg/kg 21.7, 37.0% of CPZ and 41.6, 85.6% of SBT were excreted in urine. Daily doses of about 50-90 mg/kg SBT/CPZ were administered by intravenous or drip infusion to 26 pediatric patients with acute infections such as lacunar tonsillitis, bronchitis, bronchopneumonia, suppurative diseases caused by Staphylococcus (staphylococcal scalded skin syndrome), purulent parotitis, cervical lymphadenitis, phlegmon and acute UTI related with ABPC/CPZ resistant beta lactamase producing E. coli. SBT/CPZ demonstrated the bacteriological effect on all the causative organisms. The clinical efficacy was also confirmed with the efficacy rate of 88.5%. No side effects were observed in all the cases though transient eosinophilia developed in 2 patients.