One hundred and fifty hearts of patients who died within 25 days of the onset of a clinically proven myocardial infarct were examined. Three morphologically distinct forms of myocardial necrosis were recognized. In the central and median zones of an infarct the muscle showed coagulation necrosis. Subsequently the dead tissue was obsorbed by macrophages with the preservation of sarcolemmal sheaths. Then fibroblastic collagenization of the preserved stroma occurred. Repair was not achieved by granulation tissue. Coagulative myocytolysis occurred in the outer zone of an infarct and in the non-infarcted myocardium. The dead cells were acidophilic and showed myofibrillary damage characterized by anomalous cytoplasmic band formation. Breakdown of the fibres was followed by macrophage absorption and healing as in the central area of coagulation necrosis. Colliquative myocytolysis was seen in big infarcts. It affected a narrow band of myocardial cells in the subendocardial zone or surrounding blood vessels. The fibres became oedematous and seemed to liquefy.