N,N-Diethyl-m-toluamide (m-Det) is a widely used insect repellent readily available in various formulations. Radiolabeled (14C) m-Det was evaluated for rate and extent of skin penetration in three animal species. Absorption was quantitated in excreta for 7 days following a single dermal application and deposition monitored in tissues at necropsy. The potential for transplacental transfer and bioaccumulation of absorbed m-Det the fetus was also assessed following repeated applications to pregnant rabbits. Significant dermal absorption of the repellent was noted in all species, primarily in the first few hours, and was essentially complete after 3 days. No bioaccumulation of the labeled moiety was noted in tissues at 7 days. Pregnant rabbits receiving repeated dermal applications throughout gestation showed no evidence of bioaccumulation of the chemical in maternal tissue or individual fetuses. It is suggested that m-Det should not present a dermatoxic hazard to man and that topical absorption should be less than 10% of the applied dose.