The action of a new intravenous non-barbiturate anaesthetic FBA.1420 (propanidid) has been studied in 550 patients. The period of narcotic action is short and recovery is rapid and uneventful. A brief hypotensive phase occurs during induction of anaesthesia. Coincident with the hypotension a period of hyperpnoea occurs which is usually followed by a period of respiratory depression. The respiratory depressant effect of suxamethonium was found to be enhanced by the presence of FBA.1420 but preliminary cat nerve-muscle and human electromyographic studies suggest that this interaction is not a neuromuscular phenomenon. Involuntary muscle movements were rarely marked. Laryngeal spasm did not occur but hiccough and coughing were occasional accompaniments of induction. The incidence of thrombophlebitis was low. Hepatotoxic and haematological investigations showed no significant abnormalities. The overall conclusion is that the eugenol derivative FBA.1420 is a safe short-acting intravenous anaesthetic.