Bis(trifluoromethyl) disulfide (TFD) was originally designed for use as an agricultural fumigant. Inhalation of toxic doses of TFD results in varying degrees of pulmonary edema. The purpose of this study was to determine if exhaustive exercise would potentiate the toxic effects of TFD. One group of treadmill-acclimated rats was exercised to exhaustion following a 10-minute whole-body exposure to TFD. A second group was similarly exposed but not exercised. Two other groups of rats were sham exposed; one was exercised while one remained sedentary following the sham exposure. Twenty-four hours after exposure, the animals were sacrificed; the lungs were removed and weighed, and a portion was collected for histopathologic examination. The remaining lung tissue was allowed to dry to constant weight. There was no difference in endurance times between exposed and sham-exposed rats. There was a significant increase in the amount of pulmonary edema and associated pulmonary pathology in rats exercised following exposure to TFD. Eleven of twelve animals exercised following exposure to TFD and three of twelve animals which remained sedentary following exposure died by 24 hours. The degree of pulmonary pathology in all rats exposed to TFD was profound.