This study assesses the relative prognostic value of increased left ventricular (LV) mass compared with residual ischemic myocardium and angiographic characteristics of the diseased vessel in 76 patients with uncomplicated acute myocardial infarction associated with 1-vessel coronary artery disease (CAD). All patients underwent symptom-limited treadmill exercise testing, resting and dipyridamole echocardiography and coronary angiography before discharge, and were followed-up for 32 +/- 6 months. LV measurements were obtained in diastole according to the Penn convention. Measurements of LV mass were divided by body surface area to obtain LV mass index. A cut-off value of 135 g/m2 body surface area for men and 112 g/m2 for women was prospectively selected. The individual effects of clinical, stress testing and angiographic variables were evaluated by using the Cox regression model. Echocardiographic LV mass index was increased in 43 patients and normal in 33. There was no intergroup difference with respect to baseline clinical and angiographic variables, ejection fraction and prevalence of stress-induced ischemia. During follow-up there were 23 cardiac events in the 43 patients with increased LV mass index and only 5 in the 33 with normal LV mass index (p < 0.001). No patient died or had nonfatal reinfarction among patients with normal LV mass. Cox survival analysis identified an increased LV mass index as the only independent predictor of cardiac events (chi-square = 7.9; p < 0.005; RR = 5.4). Thus, these data suggest that LV mass is an important independent risk factor in patients with uncomplicated acute myocardial infarction associated with 1-vessel CAD.