Summer and winter experiments were carried out to investigate the effects of dietary supplementation with vitamin E and vitamin C of sows in hot environments on reproductive performance, placenta transfer, piglet tissue vitamin E content and some indicators of immune status of sows and their litters. In summer, sows were given the following treatment diets: control, vitamin C 1g/day, vitamin C 10g/day, vitamin E 200 mg/kg feed, vitamin E 400 mg/kg fed, and combined vitamins (vitamin E 200 mg/kg feed + vitamin C 1 g/day). In winter, sows were given the following treatment diets: control, vitamin C 10g/day, vitamin E 500 mg/kg feed, combined vitamins (vitamin E 500 mg/kg/feed + vitamin C 10g/day). Data show that vitamin E had an effect on growth, but not on reproductive performance. Placental vitamin E concentrations were low but increased with dietary vitamin E supplementation. Vitamin E supplementation resulted in an increase in vitamin E content of sow plasma, piglet serum, colostrum and milk and piglet tissues. Supplementation with vitamin E and vitamin C had no consistent effect on parvovirus titer in sows. The relationship between sow plasma vitamin C and vitamin E concentrations and lymphocyte proliferation was not clear. Total Igs and IgG concentrations in piglet serum at weaning were significantly increased by the combined vitamin treatments. However, vitamins supplementation did not appear to have any effect in IgG colostrum. IgA concentration in milk was increased by the high level of vitamin E supplemented in the summer but not in the winter experiment.