An increase in oxidative stress and decrease in antioxidant enzymes have been suggested to be involved in the pathophysiology of myocardial infarction (MI). In this study in rats, treadmill exercise training and losartan treatment began 1 week post-myocardial infarction (MI) and lasted 8 weeks. We evaluated the changes in the mRNA and protein expressions for the enzymatic antioxidants superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase after exercise and losartan treatment post-MI. Our results demonstrated that GPx and catalase mRNA levels were comparable among all the groups, while the mRNA level for manganese SOD (MnSOD) was significantly increased in exercise training with/without losartan treatment compared with the sedentary post-MI group. Moreover, the mRNA level for gp91(phox) was dramatically decreased by a combination of exercise and losartan treatment. The protein levels for MnSOD were significantly elevated by exercise training in combination with losartan treatment. The protein levels for catalase were significantly increased in response to exercise, and further augmented by exercise together with losartan treatment. Thiobarbituric acid-reactive substances in plasma were significantly increased in the post-MI rats, but were decreased by exercise or losartan treatment, indicating that both exercise and losartan may reduce lipid oxidative damage. In addition, catalase and SOD enzymatic activities were significantly enhanced by exercise combined with losartan treatment. Our results suggest that exercise training improves catalase and MnSOD expression and attenuates oxidative stress. These effects are potentiated when combining exercise with angiotensin II receptor blockade.