Aortoenteric fistulas are a very unlikely cause of digestive bleeding. We present the case of a fifty six year old patient with a primary aortoduodenal fistula who consulted because of melena and a pulsating abdominal mass. He underwent three digestive endoscopies without arriving at any diagnosis. A computed axial tomography and an angiography showed an aneurysm of the abdominal aorta. With an exploring laparotomy a fistula was identified between the aneurysm and the fourth portion of the duodenum. An aortoaortic bypass was carried out followed by a surgical fix of the duodenum. The patient was released six days after the operation.