Clonidine is known to reduce anaesthetic requirements and improve haemodynamic stability when given as premedication. This study, of 46 ASA I-II patients undergoing thyroid surgery, was designed to assess if clonidine interferes with recovery from anaesthesia. Patients were allocated randomly to three groups to receive, 2 h before surgery, flunitrazepam 1 mg, clonidine 150 micrograms, or both drugs. Anaesthesia comprised thiopentone, alfentanil, isoflurane and 70% nitrous oxide in oxygen. Recovery from anaesthesia was assessed using a clinical score, electro-oculographic measurements and reaction times to auditory stimuli. Psychomotor tests were performed the day before surgery and 30, 60, 120 and 240 min after arrival of the patient in the recovery room. Psychomotor performance was decreased significantly after operation in the three groups (P less than 0.05) and returned to baseline at 240 min. There was no significant difference between the three groups. This study indicates that clonidine 150 micrograms orally before surgery does not delay recovery from anaesthesia.