The Simplified Acute Physiology Score (SAPS), the Acute Physiology and Chronic Health Evaluation II (APACHE II), the Acute Physiology Score (APS), and the Coronary Prognostic Index (CPI), calculated within the first 24 h of ICU admission, were compared in 76 patients with acute myocardial infarction (AMI). Sixteen (21%) patients subsequently died in the ICU. The nonsurvivors had significantly higher SAPS, APACHE II, and CPI scores than the survivors. ROC curves drawn for each severity index were in a discriminating position. There were no significant differences either between the areas under the ROC curves drawn for SAPS, APACHE II, and CPI, or between the overall accuracies of these indices. APS provided less homogeneous information. We conclude that SAPS and APACHE II, two severity indices which are easy to use, assess accurately the short-term prognosis, i.e., the ICU outcome, of patients with AMI.