Twenty-one and a half per cent of the patients with acute myocardial infarction, admitted consecutively to the coronary care unit of the University Hospitals of Leuven in the period 1973-1979, died within 28 days. The 1,669 who recovered were followed between three and nine years. The mortality rate was 13.1% during the first year and fell to below 5% in the succeeding yearly intervals. Univariate and life table analysis were performed on noninvasive, clinical data collected during the coronary care unit stay for the total population and various subgroups. The Cox proportional hazards model was applied to the data in order to determine the prognostic factors for long-term survival. Of the 34 initially selected variables, the most dominant factors were age, Killip class III and IV, peripheral vascular disease, abnormal chest x-ray findings, previous infarction, and the use of digitalis or diuretics. The model, which was validated extensively, allowed the establishment of risk categories. Mortality five years after the acute event was 8.2 times more frequent in the highest risk quintile than in the lowest one. From this study one may conclude that multivariate techniques based on noninvasive variables collected during the coronary care unit stay are valuable for the determination of the long-term prognosis of patients with myocardial infarction.