The effects of methohexital, given as a 0.1% intravenous drip in combination with nitrous oxide were studied in 159 persons who had various types of surgical operations. The depth of anaesthesia was easily controlled, the circulation remained unaffected and the combination was well tolerated. There were no difficulties concerning either induction or recovery. The combination of i.v. methohexital and nitrous oxide proved very satisfactory for maintaining prolonged anaesthesia in elderly persons and patients in poor general health.