In coronary heart disease ruptures of atherosclerotic plaques have a key position. As a rule plaque fissuring develops in the fibrous cap of a complex atherosclerotic plaque with necrotic core. In myocardial infarction in nearly all cases mural or occlusive thrombi develop as a consequence of plaque ruptures. In instable angina, too, plaques with ruptured surfaces are very numerous but often thrombi are smaller than in patients dying from myocardial infarction. Also in cases of sudden death plaque fissurings are frequently observed. Dynamic thrombi covering plaque ruptures may be sources of microemboli in the myocardium.