It has been known that there are numerous reports in Europe and America but few in Japan with regard to ulcerative colitis of which the first report was done by Wilks and Moxon in 1875, especially to segmental ulcerative colitis. This is the report of one case of our experience. The colitis was localized at right colon with typical pseudopolyposis and was undergone surgery resulting in a complete cure. Segmental ulcerative colitis tends to originate at right colon and extend toward both oral and anal directions, and it is, therefore, mandatory to resect it surgically when it is localized at right colon, so-called at the stage of the right-sided colitis. In order to fulfill it with making the early diagnosis, the x-ray examination should be very carefully done at right colon in clinically suspected case of ulcerative colitis without any abnormal finding at romanoscopic examination.