The pharmacokinetic profile of teicoplanin was studied in 12 elderly patients with a moderate degree of renal impairment (mean creatinine clearance, 51.3 ml/h/kg before treatment), after a single 6 mg/kg iv dose. Pharmacokinetic parameters were estimated both by a three-compartment open pharmacokinetic model and by non-compartmental analysis; peak plasma levels, 15 min after administration, averaged 45 mg/l. The half-lives of two distributive phases were 0.39 and 7.3 h, respectively. The elimination half-life averaged 107 h, with similar estimates obtained from the three-compartment analysis and from urinary data. The volume of distribution from the central compartment was 0.09 l/kg while the volumes of distribution at steady state and during the elimination phase were 1.3 and 1.6 l/kg, respectively. The total teicoplanin clearance averaged 10.6 ml/h/kg, with renal clearance accounting for about 40% of the total. There was a linear correlation between teicoplanin total or renal clearance and endogenous creatinine clearance. The average total recovery of teicoplanin in urine over eight days was 28%. There were no local or systemic adverse reactions to teicoplanin.