In 301 patients admitted to an intensive-care unit because of acute myocardial infarction a prognostic analysis was undertaken, based on 21 parameters (history, condition on admission, laboratory results) and related to ultimate outcome. Although some parameters were singly of prognostic value, discrimination analysis markedly improved predictive value. A prognostic index was constructed from seven easily available parameters: age, pulmonary congestion, leucocytosis, peripheral vasoconstriction, systolic blood pressure, site of infarct and hypertension. For those in a low-risk class (index less than 60, death-rate up to 5%), duration of stay in the intensive-care unit may be shortened and rehabilitation measures accelerated. Those at moderate risk (index 60-90, death-rate up to 25%) require careful monitoring. The highest risk classes (index 90-120, death-rate up to 90%; and index more than 120, death-rate more than 90%) require specially intensive and long-term monitoring, and various procedures for assisted circulation and possible cardiacsurgical intervention should be considered from the outset.