Midwives and other delivery ward personnel exposed to methoxyflurane do not have measurable traces of the agent in expired air when examined soon after exposure. This may imply a rapid uptake of the anesthetifc. If this is the case, then the products of the metabolism of methoxyflurane, such as fluoride, may appear in the urine of such personnel. The present study investigated urinary fluoride levels in 24 delivery ward personnel and compared the values found after methoxyflurane/nitrous oxide analgesia with those measured in the same individuals after exposure to nitrous oxide alone. A highly significant difference was observed. Thus it would appear that, in spite of an apparently adequate system of environmental ventilation, there is a significant uptake of methoxyflurane by delivery ward personnel when this agent is employed for obstetrical analgesia.