Prognosis after an acute myocardial infarction is closely related to the severity of coronary obstruction, and the residual functionality of left ventricle, which may be evaluated by the ejection fraction. To evaluate the utility of the ejection fraction and some cardiovascular risk factors, as predictors of a second myocardial infarction and delayed death, in those patients with a first acute myocardial infarction, 161 hospitalized patients were included in the study. The occurrence of a second myocardial infarction or death after the first month was evaluated. All patients were followed for 1 to 51 months, and the ejection fraction through a transthoracic echocardiogram was measured. 119 men and 42 women were included in the study, with a total of 3802 person-months of follow-up. The incidence rate for a second myocardial infarction was 0.01052 month,-1 and the mortality rate was 0.00342 month-1. In a Cox survival analysis model, ejection fraction was a major prognostic index and those subjects with an ejection fraction below 40% had a seven fold higher risk for a second myocardial infarction. Diabetes mellitus and hypertension were major predictors of a delayed death after a first myocardial infarction. Ejection fraction is the most related variable to the occurrence of a second myocardial infarction, and together with a history of diabetes and hypertension are good predictors of a delayed death after a first myocardial infarction. The identification of subjects with a poor prognosis may allow to establish specific preventive measures. Ejection fraction is useful to categorize patients according to their prognosis.