In a prospective 24-month trial at the Instituto Nacional de Cardiologia, 56 patients were studied. All patients had acute myocardial infarction (AMI), diagnosed by clinical, electrocardiographic and enzymatic means. They were studied in two groups: Group A with single localized AMI (n = 30) and Group B with AMI at two locations (n = 26); a resting electrocardiogram (EKG) was analyzed in each case and a low level stress test was performed within the 2nd and 3rd postinfarction weeks; coronary angiography was done between the 8th and 9th postinfarction weeks. In Group A the low level stress test (LLST) was positive for ischemia at a distance from the infarction site in 21, and eighteen of them had multi-vessel injuries (MVI); in 9 the LLST was negative; of these 7 had single-vessel injury; only the remaining 2 had MVI (p less than 0.001) with 90% sensitivity and 78% specificity. In Group B there was no significant relationship between LLST and coronary angiography (64% sensitivity, and 62% specificity). Relating the ischemic change at a distance in the resting EKG with coronary angiography, we found 75% sensitivity and 55% specificity in Group A. In Group B, sensitivity and specificity were even lower. We conclude that LLST in the early postinfarction phase in Group A is a safe and reliable method to suspect MVI, allowing the early identification of patients with lesions that could be treated by surgical means.