Glutathione peroxidase 1 (GPX-1) has an important role in antioxidant defense and has been suggested to have a protective role against the pathogenesis of atherosclerosis. In the present study, erythrocytic GPX-1 activity from 42 patients with acute myocardial infarction and 285 healthy control subjects of Taiwanese origin were determined. Our data showed that mean GPX-1 activity decreased in patients with acute myocardial infarction (40.7 +/- 9.2 vs 47.3 +/- 16.6 U/g hemoglobin; p <0.001). There was a significant inverse correlation between GPX-1 activity and acute myocardial infarction incidence (p = 0.032). In addition, plasma vitamin E inversely correlated with acute myocardial infarction incidence (p = 0.017). The incidence of acute myocardial infarction increased only in patients with low plasma vitamin E and low erythrocytic GPX-1 activity, but not in those with high vitamin E and low GPX-1 activity, low vitamin E and high GPX-1 activity, or high vitamin E and high GPX-1 activity. In conclusion, acute myocardial infarction incidence significantly increased in patients with a concomitant decrease in plasma vitamin E and erythrocytic GPX-1 activity, suggesting that both GPX-1 and vitamin E may be valuable markers for monitoring cardiovascular events, particularly when used in combination.