In spite of conventional treatment in a Coronary Unit, there is a group of patients with acute myocardial infarction who present a high mortality index. A more aggressive attitude (coronariography, angioplasty, and/or emergency coronary bypass) could improve the prognosis in some of these patients but can only be performed in a limited number of centers. In the present work, we have reviewed data obtained from the Emergency Room on 167 patients diagnosed of myocardial infarction. The variables that were correlated to mortality were: age, heart rate, blood pressure, presence of rales, radiologic heart failure cardiomegaly, ventricular extrasystoles in ECG and delay in arrival to hospital. We obtain a lineal function (z = 24.6 X1 - 0.4 X2 + 0.2 X3 + 11) which combining ventricular extrasystoles, diastolic arterial pressure, and heart rate permits to differentiate three risk groups: low, medium and high, associated to hospital mortality rates of 5.7, 36.4 and 83.3%. We suggest the use of a function of this type to select those patients who should be sent to a hospital with facilities for emergency coronary surgery.