Male C57BL/6 mice were given feed containing various concentrations of 2,4‐dichlorophenoxyacetic acid (2,4‐D), 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T) and 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) such that their diets contained daily doses of approximately 40 mg/kg 2,4‐D, 40 mg/kg 2,4,5‐T, and 2.4 μg/kg TCDD (group II); 40 mg/kg 2,4‐D, 40 mg/kg 2,4,5‐T, and 0.16 μg/kg TCDD (group III); or 20 mg/kg 2,4‐D, 20 mg/kg 2,4,5‐T, and 1.2 μg/kg TCDD (group IV). Controls (group I) were given a diet with only the corn oil vehicle added to the feed.