The protective effect of supplemental selenium, methionine, ascorbic acid, menaquinone and five antioxidants against encephalomalacia of chicks fed a diet containing dilauryl succinate was examined. Diauryl succinate induces vitamin E deficiency signs such as fragility of the erythrocytes and encephalomalacia. Supplementation of selenium and methionine with or without simultaneous supplementation of a low level of dl-alpha-tocopheryl acetate had little effect on preventing encephalomalacia. The preventive effect of ascorbic acid, methylene blue, ethoyquine, 2,6-ditertiary-butyl-p-cresol and butylated hydroxyanisole was roughly in proportion to their dietary level, and a high level of any of them could almost completely protect the chicks from encephalomalacia, while diphenyl-p-phenylenediamine was not as effective and the effect was not proportional to the dose. Menaquinone had little effect. No difference was observed in the plasma tocopherol levels and peroxide levels in the adipose tissueof the chick fed eith er dilauryl succinate or cornstarch. The effect of dilauryl succinate appears to be independent of peroxides generated in the chick.