Vitamin E supplementation enhances humoral and cell-mediated immunity, and augments the efficiency of phagocytosis in laboratory animals, farm animals, and humans. In its disease protection effect vitamin E interacts with other antioxidant nutrients and with other nutrients in the diet. Other antioxidant nutrients, such as vitamin A and beta carotene, also enhance disease resistance. Beta carotene is effective in combination with vitamin E. The optimal dose of vitamin E for maximum protection depends on many factors; thus it has to be established case by case. The delivery system of vitamin E greatly influences its effectiveness. A targeted delivery to localized immunocompetent cells in adjuvant formulations is far more effective than a general dispersed delivery in a diet. Vitamin E adjuvants provided greater immunoprotection against enterotoxemia and epididymitis in sheep than conventional vaccines.