The properties of propofol in emulsion given by continuous intravenous infusion to spontaneously breathing patients have been well studied. Thirty randomized voluntary premedicated patients undergoing dental extraction were anaesthetized with propofol (2.5 mg X kg-1 IVD, and 9 mg X kg-1 X h-1) or with propanidid (9 mg X kg-1 IVD, and 60 mg X kg-1 X h-1), supplemented with nitrous oxide in oxygen and fentanyl. Induction, maintenance and recovery times had the same characteristics. Highly significant differences occurred between the two groups regarding the increase in heart rate, apnoea and recovery time. This study showed that propofol was an eminently suitable agent for continuous intravenous anaesthesia in spontaneously breathing patients for dental surgery.