Rectal methohexitone has been used to induce anaesthesia in paediatric patients for a number of years. This study was conducted in order to confirm the safety of this method of induction for uncomplicated routine paediatric patients. Children between the ages of six months and six years were considered candidates for induction with methohexitone (10%, 25-30 mg.kg-1). Patients were monitored with a continuous oxygen saturation recording. Forty-nine patients participated in this study and anaesthesia was induced successfully in 44. The mean age of the patients was 2.7 +/- 1.6 yr. The mean weight was 13.8 +/- 4.3 kg and the mean dose of methohexitone for successful induction was 27.0 +/- 3.0 mg.kg-1. Continuous oximeter recordings were available in 31 of the 42 patients who allowed oximeter placement prior to administration of methohexitone. No major desaturation events were noted in any patient. Two brief episodes of desaturation occurred. One with a nadir of 90% which lasted for 45 sec and another with a nadir of 86% which lasted for 26 sec. Both children had their heads flexed over their parents' shoulders at the time of the event resulting in partial airway obstruction. Both of these episodes were the result of upper airway obstruction which was clinically diagnosed by the anesthetist and readily corrected by repositioning the head. This study confirms the efficacy and safety of rectal methohexitone for induction of general anaesthesia in children. Mechanical obstruction of the airway following induction seems to be the most likely cause for oxygen desaturation. Monitoring of pulse oximetry does not appear necessary provided the child is carefully observed for adequacy of air exchange.