SummaryThe interdependence of the superior and inferior mesenteric arterial systems in maintaining viability of the left colon and rectum in atherosclerotic patients is discussed.The incidence of inferior mesenteric ostial stenosis or occlusion, in atheromatous aortas, and especially in atherosclerotic aneurysmal dilatation of the aorta, is stressed.A case of gangrene of the distal two thirds of the transverse colon, left colon, rectum and anal canal, thought to be due to superior mesenteric vascular insufficiency is presented.