Deet is considered to be the best "all around" insect repellent ever developed and is the most widely used insect repellent in the world. Since its first use in a consumer product in 1956, billions of applications have been made to human skin. Information about the safety of deet comes from the human clinical literature, animal toxicology studies, and poison control centers' experiences with deet. The clinical literature reports the association of deet with neurotoxicity in 14 individuals. Three of the cases resulted in death, whereas all of the other patients completely recovered. The exact role of deet in the toxicity reported is difficult to determine from the reports. Recently reported animal safety studies have examined potential neurotoxicity following multigenerational dosing. Effects on the nervous system were only seen when generalized toxicity was also observed. Thus deet is not a selective neurotoxin. Important information about deet also comes from an investigation into the reports of adverse affects reported to 71 poison control centers in the USA. An important conclusion from this study is that there is no evidence that increasing deet concentration has any effect on the severity of the symptoms reported. The vast majority of reported cases had either no symptoms or ones that resolved rapidly. In conclusion, a thorough examination of all information available indicates that the risk of serious adverse effects following the use of deet is extremely low.