Tazobactam/piperacillin (TAZ/PIPC) was given intravenously to 15 children with acute bacterial infections including 1 with purulent tonsillitis, 11 with pneumonia, 3 with acute pyelonephritis (2 cases are omitted from evaluation because of Mycoplasma pneumonia and intramuscular injection of gammaglobulin) Daily dosages per kg bodyweight ranging from 132 to 156 mg were given in 3 divided doses per day for 4 to 7 days. Clinical responses were excellent in 7 (54%), good in 6 (46%), fair and poor in 0, with an overall efficacy rate of 100%. Good bacterial responses were obtained in all of the 8 cases from which pathogens were identified. Any side effect was not observed. The above results suggest that TAZ/PIPC is a useful new antibiotic for the treatment of bacterial infections in children.