Twenty-one critically ill children aged between 7 days and 12 years were treated with teicoplanin (three loading dosages of 10 mg/kg at 12 h intervals, followed by a maintenance dosage of 10 mg/kg/day). Serum teicoplanin concentrations were monitored by HPLC. Mean concentrations in plasma 30 min after drug administration were 20 +/- 16.1 mg/L. The volume of distribution was 0.30 L/kg and the terminal half-life was 17.41 h. Only 11% of trough values were >10 mg/L (established as desirable values). In critically ill children a dosage of 10 mg/kg/day does not assure serum trough values >10 mg/L.