In this study, we examined the effects of dietary fatty acids and vitamin E supplementation on antioxidant systems in the rat brain regions. The Sprague Dawley rats were fed the experimental diets 3-4 wks prior to the conception. Experimental diet consisted of 10% fat(wt/wt) which were safflower oil(SO, poor in $omega$3 fatty acids), mixed oil(MO, P/M/S ratio=1.03:1.45:1,$omega$6/$omega$3 ratio=6.3) and mixed oil supplemented with vitamin E(ME:MO+500mg vitamin E/kg diet). At 3 and 9 weeks of age of the newborn rats, frontal cortex(FC), corpus striatum(CS), hippocampus(H) cerebellum(CB) were dissected out from the whole brain. Activities of glutathione peroxidase(GSH-P(sub)x, superoxide dismutase(SOD) concentrations of malondialdehyde(MDA) were mesaured. Dietary fatty acids were not effective in antioxidative system for rat brain. However, when vitamin E was supplemented to the diet(ME), the activities of GSH-P(suh)x tended to increase in comparison to MO group. Therefore, the activites of GSH-P(suh)x of FC and H at the age of 3 weeks showed significant differences(p<0.05). The activities of Total-SOD tended to decrease in ME group compared to MO group. There were significant differences(p<0.05) in FC and CS at the age of 3 weeks. The activities of Mn-SOD tended to increase and Cu, Zn-SOD tended to decrease when vitamin E was supplemented. The activity levels of antioxidative enzymes at the age of 3 weeks and 9 weeks were similar. This suggested that the activity level of antioxidative enzymes reached to the adult level at the age of 3 weeks which is the end point of lactation period. The concentrations of MDA were not altered by experimental diets. When the activities of antioxidant enzymes were compared, the activities of antioxidant enzymes were the lowest in H and FC. In conclusion, the antioxidative system were not altered by dietary fatty acid at the age of 3 weeks and 9 weeks, but the supplementation of vitamin E altered the antioxidative systems. Therefore, these findings should be considered comprehensively in scope of the balance of various antioxidative systems and their interactions(Korean J Nutrition 34(1):14-22, 2001)