Patients with cardiogenic shock were arbitrarily divided into groups, those in whom shock appeared within 6 hours after the onset of acute infarction and those in whom the symptoms appeared more than 6 hours after the onset of acute infarction. The patients with more rapidly developing shock had larger areas of necrosis (average 48%) than the slow-onset group (average 28%). The former group had more sites of total occlusion of the epicardial arteries (3.5 vs 1.6) than the slow-onset group. By postmortem X-ray examination less collateral flow was visible in the rapid-onset shock patients than the slow-onset ones. These observations suggest that slow-onset shock is more likely to respond to presently available therapeutic interventions than the cases with rapid-onset shock.