This study was undertaken to evaluate the effect of 4 weeks of $alpha$-tocopherol(800 I.U./d) supplementation on oxidant stress of eleven female aerobic -majoring students during rest and exercise. Changes in the activity of the antioxidant enzyme glutathione peroxidase were also studied. Serum $alpha$-tocopherol concentration was significantly increased with vitamin E supplementation(710.1$pm$113.8$mu extrm{g}$/dl vs. 1,485,8$pm$105.2$mu extrm{g}$/dl). In addition, serum MDA concentration, an index of lipid peroxidation, significantly decreased after vitamin E supplementation. However, MDA values after exercise increased to pre-supplementation levels. Serum glutathione peroxidase activity significantly increased with vitamin E supplementation. The enzyme activity showed a trend toward decrease after exercise. Serum cholesterol values were not significantly affected by vitamin E supplementation. However, serum triglycerides significantly increased after supplementation against oxidative stress during resting periods. These supplements appraently work by decreasing lipid peroxidation and increasing glutathione peroxidase activity. However, vitamin E supplementation did not prevent exercise-induced increases in lipid peroxidation.