Military personnel are exposed to the insecticide permethrin when using the DOD Insect Repellent System. A urinary metabolite of permethrin that is in high abundance and is relatively stable may be an ideal biomarker of exposure to this pesticide. Monitoring such a biomarker can prevent over-exposure. The objectives are to identify the most abundant human urinary metabolite following dermal exposure; to utilize this information to develop rapid laboratory-based and field portable methods to monitor the degree of an individual's exposure to permethrin.