Five healthy male volunteers received over 60 sec a single intravenous injection of 400 mg of teicoplanin labelled with 41 microCi of 14C. Plasma and urine total radioactivity was measured up to 10 and 16 days, respectively. Teicoplanin was assayed in plasma and urine also by a microbiological method, with similar results. Pharmacokinetic parameters were estimated by model-independent analysis and the following mean values were obtained: elimination half-life 77 h; total body clearance 9.8 ml/h/kg; renal clearance 7.81 ml/h/kg; volume of distribution at steady-state 0.759 l/kg. Similar estimates were obtained by a compartmental analysis. A total of 80% of the administered dose was recovered in urine in 16 days; 2.7% of the dose was recovered in faeces collected for eight days after administration. The mean total recovery of the drug was 83 +/- 0.6%. The plasma and urine concentrations of teicoplanin observed after a single 400 mg iv dose exceeded the MIC for most pathogens for at least one day, and this suggests that a daily dosage regimen would be satisfactory for patients with normal renal function.