Abstract: In this paper the result of ultrastructural study of the cells of colonic adenocarcinoma of 38 patients was reported. The cancer tissue were diagnosed by the Department of Pathology. The results were as follows:1. The superficial cells of glands of human adenocarcinoma of colon showed clear-ly light and dark types, and they were chiefly columnar in shape withsome micro-villi on the free surface, 2. In the adenocarcinoma tissue there were no obviousgoblet cells. 3. The tubular glands of carcinoma were lined by a layer of radiantlyarranged light and dark cells. 4. The structure of basement membrane was fuzzyand showed increased electron density. There were also phenomena of perforation andinfiltration through the basement membrance. 5. The basal portion of the glandsconsisted of cells of different forms and structures with round and oval nuclei. In somecells there were 2 kinds of granules: the bigger ones showed diameters of 150-500nm,and the smaller ones showed diameter of 30 nm. The small granules wre closely related to disintegration of big granules, mitochondria and nuclear membrance.