More than half of some 2000 polypoid lesions of the colon and rectum studied in the Department of Pathology of Henry Ford Hospital, over a recent 5-year period, were diagnosed as adenomatous polyps. Approximately one quarter were considered non-neoplastic—hyperplastic, mucosal, and inflammatory polyps. Little evidence can be found to support a contention that any of these lesions predispose to the development of cancer; origin of carcinoma in such polyps is believed to be a rare event. The papillary or villous adenoma, on the other hand, is a potentially serious lesion. Although the incidence of progression to frank cancer does not appear great, many papillary adenomas, particularly the larger ones, contain foci of invasive cancer. Additionally, even when they do not, there is a risk of repeated local recurrence unless bowel resection is carried out. It appears that most carcinomas are carcinomas from their inception.