The hospital courses of 882 consecutive patients with acute myocardial infarction admitted to the coronary care unit (CCU) during a 3-year period were evaluated. Their courses after discharge from the CCU were assessed with reference to the following serious complications which had occurred during their stay in the CCU; ventricular tachycardia or fibrillation, second-or third-degree heart block, pulmonary oedema, cardiogenic shock persistent sinus tachycardia, persistent hypotension, atrial flutter or fibrillation, or extension, or extension of infarction. Of the 494 patients (56%) with one or more of these complications, 38 (8%) died of cardiac causes in hospital after transfer from the CCU. Of 388 patients (44%) in the uncomplicated group, only 2(0,5%) died of cardiac causes after transfer from the CCU. The same patients were classified according to the Coronary Prognostic Index (CPI) of Norris. None of the 54% of patients with a CPI of less than 6 units died in hospital after transfer from the CCU. It is proposed that patients with a CPI of less than 6 units and with none of the listed serious complications during their CCU stay could safely be discharged from hospital earlier than is customary.