The course of 100 consecutive patients with proven acute myocardial infarction admitted to medical wards at Denver Veterans Administration Hospital (VAH) were compared with 105 monitored in a coronary care unit at Colorado General Hospital (CGH) over a 17-month period. Clinical characteristics and electrocardiographic features were similar in the two groups and care was by identical physicians. Arrhythmias were observed in 80% of monitored patients and 58% at VAH. Ventricular fibrillation in "good risk" patients occurred in 9% at CGH and 19% at VAH. Fifty-seven percent of monitored and 12% of unmonitored patients were resuscitated and survived. Resuscitation of all first week cardiac arrests occurred in 37% and 4% of the patients respectively. Total mortality at VAH was 33% and at CGH, 19%. Results stress the value of coronary care units in prevention of ventricular fibrillation and increasing successful resuscitation.