To determine whether vitamin E (dl‐α‐tocopherol) supplementation could protect against short‐term respiratory responses to O3exposure its effects were investigated in young healthy adult volunteers. Experimental groups received 800 or 1600 IU vitamin E per day for 9 or more wk, while control groups received placebo. Subjects were then exposed for 2‐h periods to 0.5 ppm O3, with secondary stresses of heat and intermittent light exercise. Responses to O3exposure, evaluated in terms of symptoms, forced expiratory performance, and single‐breath nitrogen washout, were not significantly different between vitamin E and placebo groups.