Among approximately 1,700 polyps of the large bowel and rectum removed surgically there were 61 adenomatous polyps containing carcinoma and 81 villous adenomas with and without carcinoma. In the adenomatous polyps the incidence of both atypia and invasive carcinoma rose sharply with increase in size. No lymphnode metastases were found associated with the 61 adenomatous polyps containing carcinoma, and in no instance did the lesion cause the death of the patient. However, 45 (55%) of the 81 villous adenomas contained invasive carcinoma; in 13 of the 45, the carcinoma had involved the regional nodes and in 10 instances had killed the patient. In a separate study of 666 clinically frank carcinomas, areas of adenomatous polyp were found in 6. The authors urge that all polypoid lesions be removed for definitive histologic study unless the operative risk is prohibitive.