A morphological study on the coronary ostia was performed in 70 autopsied human hearts, with particular attention focused on its funnel-shaped structure, its aging changes and relation to atherosclerosis. The following results were obtained in this study, 1) There are great varieties in the funnel-shaped structure of the coronary ostia. However, a double circular shape in the right ostium, and a comet shape in the left are commonly seen. 2) The funnel-shaped structure of the coronary ostia is characterized by longitudinal smooth muscle arrangement in the inner layer and circular in the outer one. 3) Atherosclerosis and the overhang phenomenon tend to be more severe in the right ostium than the left. 4) The incidence of significant ostial stenosis due to atherosclerosis is : 7 out of 70 cases in the right ; 3 in the left, and 4 cases in both sides. Among 14 cases of ostial stenosis, there are 4 cases of myocardial infarction. Thus, the incidence of myocardial infarction is more common in cases of ostial stenosis than in those without stenosis. 5) In ischemic heart diseases, not only sclerotic changes in the coronary arteries themselves, but changes in the ostia of the coronary arteries should be given serious consideration.