In a group of 701 patients with acute myocardial infarction treated in the intensive care unit from 1969 to 1976 557 ((79,5%) had a transmural infarction. The clinical course in these patients was significantly more aggravated by haemodynamic complications especially left and right heart failure and cardiogenic shock. The pericarditis appeared with an incidence of 10,4% as complication of transmural myocardial infarction only. Atrioventricular block, supraventricular ectopies, ventricular fibrillation and intraventricular disturbance of conduction occurred more frequently in patients with transmural myocardial infarction. Corresponding to the larger size of infarction the maximal average rise of serum enzymes (SGOT, CPK) was observed in this group. The hospital mortality was 28,2%, compared to 11,2% of the patients with nontransmural infarction.