A review of the biodistributionand foxicityof the insect repellentN,N‐diethyl‐m‐to‐luamide (DEET) is presented. Workers using repellent containing this compound may be exposed to greater than 442 g in 6 mo. In human studies, variable penetration into the skin of from9 to 56% ofatopically applied dose and absorption into the circulatory system of approximately 77% have been reported. Excretion of DEET by humans was initially rapid but not as complete as in animal models. Only about one‐half of the absorbed DEET was excreted by humans over 5 d. Depot storage of DEET in the skin was also documented. Skin irritant effects, including scarring bullous dermatitis in humans, were reported. One animal study that reported embryotoxicity could not be confirmed by other investigators. The limited testing for mutagenicity and carcino‐genicity provided negative results. Neurotoxic effects were observed in workers exposed to 4 g or more per week. Six young girls developed encephalopathies after exposure to unspecified amounts of DEET ranging from small to massive doses. Three of these girls later died. The cause of their death has not been resolved. Because of the lack of information, further research into the absorption, carcinogenicity, and neurotoxic effects is needed.