Two techniques of anaesthesia have been compared. The first (control group) consisting of premedication with hyoscine 0.6 mg, induction with thiopentone 250 mg and suxamethonium 100 mg, and maintenance with 67 per cent nitrous oxide with oxygen (using a Howells ventilator) and a suxamethonium infusion. In the study group exactly the same technique was used with the addition of methoxyflurane (0.1 per cent) after delivery of the infant by elective or emergency section or vaginally, or throughout the operation of postpartum sterilization. Attention has been focused on the incidence of awareness and dreaming during operation. It has been demonstrated that the introduction of methoxyflurane into the standard technique, in the manner described, results in a marked reduction in the incidence of awareness and a marked and significant reduction in the incidence of unpleasant dreams. Some of the implications of this modification are discussed.