SUMMARY Sixty-four patients received methoxyflurane analgesia and/or anaesthesia for labour and delivery. Analgesia with methoxyflurane-air produced satisfactory analgesia for labour and delivery in the multigravidae of Group I. Foetal and maternal blood levels did not increase with increased duration of inhaler use, apparently due to the absence of pain-induced hyperventilation. Patients in Group II required the addition of light methoxyflurane, nitrous oxide and oxygen anaesthesia. This resulted in the highest foetal memoxyflurane levels of the three groups, and the highest rate of neonatal depression. Group III patients arrived with delivery imminent, and were given light methoxyflurane, nitrous oxide and oxygen anaesthesia. Despite high maternal levels of methoxyflurane, foetal levels were no higher than in Group I, presumably because of the short duration of exposure. Methoxyflurane has little effect on the foetus if low concentrations are administered to the mother, or if the duration of higher concentrations is kept short.