We prospectively investigated criteria to identify patients in the early phase of acute myocardial infarction at risk for significant left ventricular (LV) dilation 1 year after myocardial infarction. In 54 patients receiving thrombolysis within 4 hours after onset of symptoms, the end-diastolic volume index (EDVI) and the end-systolic volume index were assessed by two-dimensional echocardiography initially (within 23 +/- 21 hours) and 1 year after myocardial infarction. After 1 year, LV dilation occurred in 51 patients (94%) and was significant (> mean normal value + 2 SDs) in 14 patients (26%). Significant univariate predictors (p < 0.05) for LV dilation were age, anterior myocardial infarction, initial EDVI and end-systolic volume index, enzymatic infarct size, LV end-diastolic pressure, and mitral regurgitation. No other variables obtained from clinical information, two-dimensional echocardiography, or angiography, including residual coronary perfusion or stenosis, had predictive value. The optimal multivariate predictive model was the combination of the initial EDVI and the enzymatic infarct size, which correctly predicted significant LV dilation in 12 of 14 patients and falsely in eight of 39 patients (sensitivity 86%; specificity 79%). Patients at risk for significant LV dilation 1 year after myocardial infarction were identified adequately 3 days after myocardial infarction by the combination of the initial echocardiographic assessment of EDVI and the enzymatic infarct size. Thus a simple method could facilitate the selection of patients for intervention after acute myocardial infarction.