Anastomotic dehiscence after colon resection is the most frequent complication in colon surgery and the main cause of post-operative death. In the light of anatomical peculiarities of the blood supply to the rectum, it would appear that in atherosclerotic patients with impairment of hypogastric arteries (80% in authors' series out of 200 atherosclerotic subjects) inferior mesenteric artery ligature, determining vascularization of the rectal ampulla by the distal vessels alone, results in an insufficient supply in case of colo-rectal anastomosis. A series of 15 cases of cancer of the left and sigmoid colon, treated with left hemicolectomy, preservation and peeling of the inferior mesenteric artery, is reported. In the follow-up ranging from 6 months to 5 years, no anastomotic dehiscence was observed and only one case (7.5%) presented hepatic recurrence after two years. The other patients are all alive and disease free.