In view of the sparsity of report on normal and abnormal pattern of the major arteries during fetal life, the authors undertook investigation of the aortas, coronary arteries, renal arteries, and the umbilical arteries of 76 korean fetuses, ranging from 2¹/2 months to full-term, A normal pattern and its evolution of the intima, media, and the adventitia was described. The P. A. S. positive substance was most abundantly found in the media of the umbilical arteries, medium amount in the media and intima of the renal arteries and the aortas, and lesser amount in the media of the coronary arteries. A surprisingly high incidence of the alteration of the internal elastic membrane of the aorta simulating to the early lesions of atherosclerosis in adult and neonatal life was observed. In e1even instances, microcystic degeneration of the inner media of the aorta was observed, and its relationship to the idiopathic cystic medial necrosis and dissecting aneurysm was discussed.