Fentanyl kinetics were studied in patients with cirrhosis and in patients with normal hepatic and renal function undergoing surgery under general anaesthesia, the latter group served as the controls. Plasma fentanyl concentrations declined bi-exponentially in the controls with an average elimination half-life (T½β) of 263 mm; total plasma clearance (C7) was 10.8mlmin−1kg−1, and total apparent volume of distribution (Vβ) 3 81 litre kg−1. No significant change was observed in patients with cirrhosis: T( T½β) was 304mm, Cl 11.3 ml min−1 kg−1 and Vβ 4.41 litre kg−1. These data suggest that the elimination half-life of fentanyl is not primarily influenced by the rate at which it is metabolized in the liver.