Plasma concentrations of alphaxalone have been measured during various rates of continuous infusion of Althesin used to supplement nitrous oxide-oxygen anaesthesia in man. There was an approximately linear relationship between the plasma concentration of alphaxalone and the rate of infusion of Althesin. The rate of uptake of alphaxalone into the liver did not appear to be impaired in the presence of the steroid myoneural blocking agent pancuronium, or in patients with hepatic cirrhosis.