The microvasculature of human myocardium was examined stereoscopically after the injection of Silicone rubber. Material were 40 normal hearts, three of infants, one of child, and 36 of adults, ranging in age from 27 to 79 years. Three types of arteries, subepicardial, branching, and straight type arteries, were confirmed. The microvascular pattern of left ventricular free wall, the posterior wall of the left ventricle, interventricular septum, right ventricular free wall, papillary muscles, trabeculae carneae, infant heart, and aged heart were also examined. The present study revealed that the inner one-third zone was supplied by the terminal branches of both branching and straight type arteries. In infant heart, the inner zone was wider than that of the adult. In the aged cases, reduction in filling with patchy deficit often appeared in this inner zone. The finding of the aged change was probably caused by the characteristic microvascular pattern, and this suggested that the same anatomical mechanism might commit myocardial infarction.