Fluoride concentrations in maternal and fetal benes were measured following exposure of pregnant rats to methoxyflurane or enflurane anesthesia. Fluoride content in fetal bone increased significantly only after exposure to methoxyflurane, and then only when methoxyflurane was administered after 12 days of gestation, when ossification of fetal bone begins. Fluoride concentrations in maternal bone increased following both anesthetics, except in rats exposed to methoxyflurane after 15 days of gestation, when ossification of many fetal skeletal parts is in progress and fluoride is preferentially deposited in the fetal skeleton.