Conjugated linoleic acid (CLA) is a collective term for the positional and geometric isomers of a conjugated diene of linoleic acid (C18:2, n-6). The aims of the present study were to evaluate whether levels of hepatic a-tocopherol, a-tocopherol transfer protein (a-TTP), and antioxidant enzymes in mice were affected by a CLA-supplemented diet. C57BL/6 J mice were divided into the CLA and control groups, which were fed, respectively, a 5% fat diet with or without 1 g/100 g of CLA (1:1 mixture of cis-9, trans-11 and trans-10, cis-12) for four weeks. a-Tocopherol levels in plasma and liver were significantly higher in the CLA group than in the control group. Liver a-TTP levels were also significantly increased in the CLA group, the a-TTP/b-actin ratio being 2.5-fold higher than that in controlmice (p<0.01). Thiobarbituric acid-reactive substances were significantly decreased in the CLA group (p<0.01). There were no significant differences between the two groups in levels of three antioxidant enzymes (superoxide dismutase, glutathione peroxidase, and catalase). The accumulation of liver a-tocopherol seen with the CLA diet can be attributed to the antioxidant potential of CLA and the ability of a-TTP induction. The lack of changes in antioxidant enzyme protein levels and the reduced lipid peroxidation in the liver of CLA mice are due to a-tocopherol accumulation.