Aneurysm of the inferior mesenteric artery is rare. Often unrecognized unless complicated, it is, today, demonstrated by sonography or tomodensitometry and confirmed by angiography. Usually observed in patients with atheroma, it presents a mechanical origin secondary to a "jet disorder" phenomenon occurring in an artery with a hyper-output, responsible for almost the entire gastro-intestinal vascularization. The prevention of its dangerous complications (rupture or thrombosis) justifies a systematic procedure usually requiring, in addition to the excision of the aneurysm, a revascularization of the digestive arteries, as in the case presented here.