The clinical management of acute myocardial infarc-tion and crescendo angina as well as the prevention of sudden ischaemic death require accurate knowledge of the underlying arterial pathology. It is on just this aspect that until recently there has been disagreement particularly among pathologists. Inbrief, this controversy was concerned with whether coronary artery thrombi were or were not directly responsible for all three clinical pictures of acute ischaemia. Resolution of the controversy has been derived from coronary angiography in life in patients with acute infarction and crescendo angina and from detailed pathological studies. These latter studies dif-fer from many carried out previously by the use of postmortem coronary angiography and histological reconstruction of the microanatomy of occlusive lesions.