Secondary aortoduodenal fistula is a rare and life-threatening long-term complication of abdominal aortic surgery. Pathogenesis is often not clear; both mechanical trauma and septic procedures are involved as principal factors. The interval between first intervention and development of the fistula can vary from months to years. The presentation is often subtle with a herald bleeding followed by a period of grace, followed or not by an exsanguinating hemorrhage. The right diagnosis of aortoduodenal fistula hemorrhage can be difficult. We emphasize the need to have an early and correct diagnosis in one with differential diagnosis of patients with gastrointestinal bleeding after previous abdominal aortic replacement surgery. The esophagogastroduodenoscopy (until the Treitz) is the main diagnostic procedure, able to demonstrate the fistula and rule out other possible causes of bleeding.