Pathological findings in the heart and particularly in the coronary arteries are reported from 70 patients dying from pump failure after acute myocardial infarction. Fifty of the patients had died in cardiogenic shock, the remainder from refractory congestive heart failure. Three-vessel disease (greater than or equal to 75% occlusion) was present in 68 per cent of the group with cardiogenic shock but in only 35 per cent of those with fatal congestive heart failure (P less than 0-02). In both groups there was an almost equal incidence (84% for cardiogenic shock and 80% for congestive heart failure) of severe disease (greater than or equal to 75% occlusion) over a long segment of the left anterior descending artery. However, there were differences between the two groups regarding the involvement of the other coronary arteries. Whereas patients with cardiogenic shock generally showed severe disease over a long segment in all coronary arteries, in 60 per cent of those with congestive heart failure there was only local severe narrowing of the right coronary artery with little or no narrowing of the peripheral part. Similarly, 60 per cent of those with congestive heart failure had less than 75 per cent narrowing in the left circumflex artery. These anatomical findings may be of relevance with regard to desirability of acute coronary bypass surgery in patients with pump failure after acute myocardial infarction.