The successful management of aortoenteric fistula (AEF) requires early diagnosis. To evaluate the accuracy of our diagnostic approach, the hospital course of seven patients with AEF was reviewed. In six patients, the initial bleeding episodes were of the low volume type characterized by hematemesis and melena or by melena alone. All patients were febrile. In six patients, blood cultures obtained preoperatively were positive for enteric organisms identical to those found in cultures obtained intraoperatively from the AEF site. Roentgenographic examination of the upper gastrointestinal (GI) tract performed in three patients was diagnostic for AEF in only one. Endoscopy in seven patients revealed a bleeding suture line in one. Angiography was not diagnostic in the six patients in whom it was performed. When patients are seen with the triad of GI bleeding, a history of aortic surgery, and fever, aerobic and anaerobic blood cultures should be obtained. If blood cultures are positive for enteric organisms, the diagnosis of AEF should be strongly suspected, and early surgical intervention is indicated.