Halothane-reactor and non-reactor pigs were offered diets containing either 10 or 135 I.U. vitamin E kg−1 ad libitum for 6 weeks. There were no differences in food intake or weight gain between groups. The fat contents of the semi-tendinosus, gluteus medius and serratus muscles of reactors were significantly less than those of non-reactors irrespective of dietary vitamin E content. Vitamin E supplementation of diets significantly elevated plasma and tissue vitamin E concentrations of both reactors and non-reactors. However, after vitamin E supplementation, significantly higher vitamin E concentrations were found in muscles of reactors compared to non-reactors. A similar trend was apparent when the tissues of non-supplemented reactors and non-reactors were compared. There were no indications of antioxidant enzyme deficiencies in reactors. Plasma pyruvate kinase and creatine kinase activities did not discriminate between reactors and non-reactors. However, after application of a standard pharmacological stress (neostigmine bromide), plasma pyruvate kinase activities of reactors were higher than those of non-reactors irrespective of vitamin E supplementation of the diet. The possibility that vitamin E function is compromised in stress susceptible pigs, and that this may be compensated for by dietary vitamin E supplementation, is discussed.