We examined how dietary supplementation of vitamin E protects against liver oxidative damage in rats with water-immersion restraint stress (WIRS). Before WIRS exposure, rats received a normal diet (ND) or vitamin E-supplemented diet (VESD) (500 IU alpha-tocopherol/kg diet) at a mean dose of 15 g/animal/d for 4 wk. The two diet groups had serum transaminases and lactate dehydrogenase activities and adrenocorticotropic hormone, corticosterone, and glucose levels to a similar extent. VESD-fed rats had higher liver a-tocopherol concentrations and lower liver ascorbic acid, total coenzyme Q(9) (CoQ(9)), reduced CoQ(9), reduced CoQ(10), and lipid peroxide (LPO) concentrations than ND-fed rats. When the two diet groups were exposed to 6 h of WIRS, the serum liver cell damage index enzyme activities increased more greatly in ND-fed rats than in VESD-fed rats but the serum stress marker levels increased to a similar extent. The WIRS exposure caused no change in liver LPO concentration with the further increase in liver a-tocopherol concentration in VESD-fed rats but increased liver LPO concentration without changing liver alpha-tocopherol concentration in ND-fed rats. Upon the WIRS exposure, liver reduced glutathione concentration decreased with the further decrease in liver ascorbic acid concentration in VESD-fed rats and those concentrations decreased in ND-fed rats. The WIRS exposure recovered the decreased liver total CoQ(9) and reduced CoQ(9) concentrations in VESD-fed rats but decreased liver total CoQ(9), reduced CoQ(9), and reduced CoQ(10) concentrations in ND-fed rats. These results indicate that dietary vitamin E supplementation protects against liver oxidative damage without affecting the stress response in rats with WIRS.