Histologic and polarization-microscopic studies of the cardiac infarct area in 64 persons who had died several hours to 3 weeks following an angina attack led to the identification of three types of dying for cardiac muscle cells on the basis of a morphologic criterion (state of myofibrils), described as relaxational, contractional, and lytic, respectively. The cells showing these different types of dying differed with regard to time of appearance, frequency of occurrence, and location in the lesional area, which suggested that each of the three types of dying occurs by a distinct mechanism.