In the present study, the effects of long-term exogenous glucocorticoids administration and dietary supplementation of alpha-tocopheryl acetate on the induction of lipid peroxidation in skeletal muscle were investigated. Male broiler chicks were randomly assigned to 2 diet treatments: the basal diet supplemented with 20 (low level of vitamin E) or 200 (high level of vitamin E) mg of vitamin E (as DL-alpha-tocopheryl acetate)/kg of diet. At 35 d of age, the chickens in each dietary treatment were randomly divided into 3 groups of 30 chickens and subjected to the following treatments: daily s.c. injection of dexamethasone (DEX, 2 mg/kg of BW) for 6 d, sham injection of saline (control), or the sham-treated pair-fed control that maintained the same feed intake as DEX treatment (pair-control). The results showed that the growth of chickens was suppressed by DEX, whereas it was improved by the high level of vitamin E treatment. The DEX treatment resulted in augmented plasma concentrations of TBA reacting substances. Muscle TBA reacting substances levels were higher in DEX chickens at both 24- and 48-h time points postslaughter. Vitamin E supplementation suppressed the formation of lipid peroxidation in both plasma and skeletal muscle tissues. Muscle activity of superoxide dismutase was significantly increased by DEX treatment in both musculus pectoralis major and musculus biceps femoris and maintained as such during the initial 48 h postmortem. The result of the present study indicated that DEX treatment increased the saturation level of skeletal muscle fatty acids. These results suggest that vitamin E supplementation was favorable for the performance of broiler chickens by alleviating the oxidative stress induced by DEX treatment.