The effects of dietary restriction of vitamin E and selenium were studied in male Long-Evans hooded rats. Weanling animals were maintained for 5-6 weeks on torula yeast-based diets, with or without the addition of vitamin E (150 IU/kg) or selenium (0.5 mg/kg), to form the following dietary groups: +E, +Se; +E, -Se; -E, +Se; -E, -Se, and a fifth group pair-fed with the -E, -Se group. This latter group exhibited a decreased rate of growth similar to the -E, -Se group. Lymphocyte blastogenesis in response to mitogens was decreased in animals fed the diets deficient in either vitamin E or selenium, and also in the pair-fed group. Very marked suppression of mitogen responses was seen in the doubly deficient group, as well as a greater loss of viability during culture. Spleen cell-mediated antibody-dependent lysis of chicken erythrocytes was increased in the doubly deficient group, although this difference could be abolished by the addition of catalase, but not indomethacin, to the culture medium. Dietary deficiency of vitamin E and selenium had no discernible effects on alveolar macrophage function, as measured by cell-mediated antibody-dependent cytolysis, killing of Staphylococcus aureus or regulation of T-lymphocyte blastogenesis.