A 74-year-old male patient was operated in Vakif Gureba Hospital for aortoduodenal fistula developing from abdominal aortic aneurysm. The patient was diagnosed as abdominal aortic aneurysm after physical examination and computed tomography in another center. Appearing of melena and hematemesis gastroduodenoscopy and radionuclide scanning was performed as diagnosis. After 6 days gastrointestinal bleeding recurred in massive haemorrhage and the patient was operated with a diagnosis of aortoenteric fistula as emergency. A midline laparotomy was performed. There was a fistula between infrarenal abdominal aortic aneurysm (with diameter 8x10 cm) and the 3rd portion of the duodenum. The duodenum was resected segmental and the fistula was disconnected. Following aneurysmotomy a prosthetic graft was placed in the aortobiiliac position. The patient was discharged at the 42nd postoperative day. Primary aortoenteric fistula is a very rare con sequence of untreated abdominal aortic aneurysm. The segments of intestine most frequently involved in aortoenteric fistula are the 3rd and 4th portions of the duodenum. Clinical presentation is recurrent episodes of gross gastrointestinal haemorrhage. These cases have high mortality and morbidity unless evaluated as quickly as possible and appropriate surgical intervention performed.