Abstract The routes and methods of cancer dissemination in lesions of the colon, rectum, and anus have been discussed, and a review of the vascular and lymphatic supply to the area has been made with special reference to the advisability and practicality of ligating the inferior mesenteric artery at its aortic origin. Ninety cases of distal bowel resections for cancer with a high ligation of this artery have been presented, and the findings in the cleared specimens reviewed. Sixty per cent of these cases revealed positive lymph nodes, 17.8 per cent of which were located at the origin of the inferior mesenteric artery. Three cases of squamous cell carcinoma of the anus failed to exhibit nodal metastases, but the malignant mesenchymoma of the low rectum did involve a regional node. All the rectal lesions initiated an orderly pattern of lymphatic spread, but the sigmoidal lesions in at least 2 cases revealed a skip pattern. No correlation was attempted between the presence of high positive nodes and lateral lymphatic spread. In at least 8 cases, a ligation of the inferior mesenteric artery below the left colic branch would not have removed positive nodes in the upper portion of the mesentery. Thus, 9 per cent of the operative procedures would have been failures without a high ligation.