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) to provide 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); and 20 mg/kg 2,4‐D, 20 mg/kg 2,4,5‐T, and 1.2 μg/kg TCDD (group IV). The chemical mixtures were chosen to approximate the concentrations of the components of Herbicide Orange. Controls (group I) were given a diet with only the corn oil vehicle added to the feed. In the treated animals, liver enlargements, hepatocellular toxicity, and reduced thymus size were found and body weight gain was significantly less than that of the control animals. Significant or complete recovery from liver and thymus toxicity was observed when the mice were returned to a control diet. The thymic toxicity and hepatotoxicity seemed to be related to TCDD levels, while the decrease in body weight gain was more closely associated with phenoxy acid concentrations. All effects attributed to the mixture were elicited by individual compounds in the mixture in previous studies.