The regulation of normal oxidative balance include the maintenance of adequate levels of dietary antioxidants such as vitamin E. The objective of this investigation was to study the effect of three different dietary levels of vitamin E (normal, supplemented 20 times higher and deficient) on plasma and liver lipid peroxidation, assayed by determination of thiobarbituric acid reactive substances (TBARS) and vitamin E in plasma and liver and hepatic reduced glutathione. Administration of dietary vitamin E caused a dose-dependent increase in liver and plasma concentration of this vitamin to 42.11 micrograms/g liver and 29.52 mumol/l respectively, in the supplemented group, and a low concentration of TBARS, 0.67 nmol/mg protein, in liver. The group receiving the diet without vitamin E showed high values of hepatic TBARS, 2.95 nmol/mg protein, and low values of reduced glutathione and reduced concentration of hepatic and plasma vitamin E (1.75 micrograms/g liver and 3.67 mumol/l, respectively). In conclusion, the vitamin E deficiency alone induces the liver lipid peroxidation in rats, and maintenance of adequate or higher vitamin E levels acts as a protective factor against free radical generation.