Tocopherol, one of the antioxidants in vegetable fats and oils, was added to the autoxidized diet of male rats at the same tocopherol level as soybean oil before autoxidation. Autoxidized soybean oil was used as the test lipid; fresh soybean oil was the control. The diet containing autoxidized oil depressed the body weight gains and increased the tissue ratios to body weight, with the exception of testicle. Parallel with those, increased hemolysis, peroxide value and carbonyl value in the tissue lipids, and a decrease in linoleic or arachidonic acid was observed. The effect of dietary vitamin E on the tissue lipid peroxidation was different among the individual organs. From the results obtained by chemical analyses, the lipid peroxidation caused in the liver, heart and intestine was recognized to be suppressed effectively when the same tocopherol level as fresh soybean oil was added to the diet.