We collected more than 400 fetuses at different ages. out of them 120 cases were taken randomly whose ages ranged from 3 to 9 months. They were divided into 8 groups according to the age. Sections were made from the left and right coronary arteries where atherosclerosis occurs most commonly.All sections were stained with hematoxylin-eosin, Weigert-VG mixture,Masson' s trichrome and Alcian Blue-PAS,In addition, some of them were stained with fat and mucins.The results were as follows:1.Early changes of coronary atherosclerosis of the foetuses at different ages.①Fat spots and fatty streaks. We believe that they can develop into atherosclerosis or stop developing or subside,②Proliferation focuses of smooth muscle cells.Smooth muscle cells are the main elements of pathological changes of atherosclerosis, participating in the formation of atherosclerosis.③Smooth muscle cells can produce fibrous connective tissues and mucopolysac charide in the walls of coronary arteries. The above mentionded findings in the fetuses are of great significance in exploring the occurrence and development of atherosclerosis.2.1～Ⅱ grade positive pathological changes of coronary atherosclerosis were found in the fetuses.It protruded from the media through the intima into the vascular cavities, occupying 255 or more of the cavity.It had made the vascular cavities narrow to a degree of 1～Ⅱ grade. It is not easy to subsidecompletely. The living conditions and environments of the fetuses are simpler than that after their birth, and these are of specific importance in studying the etiology and pathogenesis of atherosclerosis.Since the nourishment of the fetuses are supplied by the blood of the mothers' uteri, whether the early pathological changes in the coronary artery and Ⅰ ～Ⅱ grade positive pathological changes of the fetuses are due to the hyperlipidemia of their mothers or the hereditary factors needs to be studied.