A single dose of 6 mg/kg teicoplanin was infused over 10 min in six children of mean age 7 years, and a single dose of 6 mg/kg was infused over 20 min in four neonates of mean age 8.5 days. Serum sampling was performed at 0 and 10 min and at 1, 4, 12 and 24 h and thereafter 24-hourly, up to ten days. Urine was collected for each 24 h throughout the study in children. Teicoplanin was assayed by high performance liquid chromatography. Tolerability of teicoplanin was excellent both in children and in neonates. For all the patients the serum concentrations of teicoplanin followed an open two-compartment model. Mean Cmax was 48.6 +/- 16.7 mg/l (10 min) in children, and 19.6 +/- 1.05 mg/l (20 min) in neonates, and mean t1/2 beta was 20.5 +/- 5.5 h and 30.3 +/- 6.3 h, respectively. On the basis of the results dosage recommendations for children and neonates are made.