In this study, the ratio of 6 g -hydroxycortisol (6 g -OHF) to free cortisol (F) was determined in urine following a single dermal dose of 400 mg/kg of DEET ( N,N -diethyl- m -toluamide), and 1.3 mg/kg of permethrin, alone and in combination, in rats. Urine samples were collected at 2, 4, 8, 16, 24, 48, and 72 h after application. Recoveries of 6 g -OHF and cortisol (F) from control urine samples were between 75 and 85%, with limits of detection at 30 and 10 ng/ml for cortisol and 6 g -OHF, respectively. A single dermal dose of DEET alone and in combination with permethrin significantly increased urinary excretion of 6 g -hydroxycortisol 24 h after dosing. Permethrin did not significantly alter the urinary excretion of 6 g -hydroxycortisol. These results indicate that DEET, alone and in combination with permethrin, increased urinary excretion of 6 g -OHF in rats following a single dermal dose application.