A report is based on the investigation of the hearts of persons who died at an early ischemic (up to twenty-four hours) stage of the acute myocardial infarction studied under the light microscope (39 cases) and at the ultrastructural level (5 cases). An original technique of the combined filling of the macro- and microvascular bed was applied as well as the intravascular silver impregnation and special histologic methods for detection of the early lesions of cardiomyocytes were used in some cases. The interrelationship and sequence of lesions of the coronary arteries and vessels of the cardiac microcirculatory bed are shown. The lesions of microvessels bear mainly a secondary character and depend upon the duration of myocardial infarction, its dimensions and its deepness. The ultrastructural alterations of microvessels are characterized by the heterogeneity and dependence on the degree and character of the cardiomyocyte lesion. A morphological estimation of the compensatory-adaptive alterations in the cardiac vascular bed at the early stages of myocardial infarction development is given.