Effects of dietary fatty acids and vitamin E on antioxidant system were studied in rat liver and serum. Sources of dietary fat (10 wt%) were safflower oil (SO) poor in $omega$3 fatty acid and mixed oil (MO) with computer-adjusted fatty acid ratios (AA/DHA=1.4, $omega$6/$omega$3=6.3, P/M/S=1.0/l.5/1) with (ME) and without (MO) vitamin E (500 mg/kg diet). Rats were fed the three kinds of diet from 3~4 wks prior to the conception. At the age of 3 and 9 wks of the second generation rat, antioxidant vitamins and glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) activities were measured in the liver and serum. The concentrations of $eta$-carotene were lower in ME than in MO and SO in the liver at the age of 3 wks. It seemed that vitamin E has an inhibitory action on the uptake of $eta$-carotene or acts as a preferred antioxidant to $eta$-carotene. The concentrations of lycopene were lower in SO than in MO in the liver at the age of 3 wks. The concentrations of cryptoxanthin showed no significant changes within groups. The activities of GSH-Px tended to increase in ME compared to MO and the ratios of SOD/GSH-Px tended to decrease in ME compared to MO in the liver at the age of 3 weeks. The activities of antioxidant enzyme at the age of 3 weeks and 9 weeks were similar. This suggested that the activity level of antioxidant enzymes reached to the adult level at the age of 3 weeks which is the end point of lactation period.