Intravenous ampicillin-sulbactam is effective in the treatment of various infections in adults, but little is known about the pharmacokinetics (PK) of ampicillin-sulbactam in children. The objective of this study was to determine the PK of ampicillin and sulbactam in pediatric patients with intra-abdominal infection, skin and/or skin structure infection, or periorbital-preseptal and facial cellulitis. Intravenous ampicillin and sulbactam (2:1), 40 to 80 mg/kg of body weight, were given every 6 h for 2 to 6 days to 28 pediatric patients. The ages ranged from 1 to 6 years for 10 patients, 6.1 to 10 years for 9 patients, and 10.1 to 12 years for 9 patients. Multiple blood samples were obtained and analyzed for ampicillin and sulbactam in plasma and serum by high-performance liquid chromatography. The mean maximum concentration of drug in serum ranged from 177 to 200 µg/ml for ampicillin and 82 to 102 µg/ml for sulbactam in the three age groups. The mean total clearance, steady-state distribution volume, and half-life were 4.76 ml/min/kg, 0.32 liter/kg, and 0.77 h, respectively, for ampicillin and 4.95 ml/min/kg, 0.34 liter/kg, and 0.81 h, respectively, for sulbactam. Dose or gender did not affect the PK of ampicillin or sulbactam. The PK of ampicillin and sulbactam in these patients were comparable to those reported in adults. The combination was well tolerated in pediatric patients.