Primary aortoduodenal fistula is an uncommon cause of massive upper gastrointestinal hemorrhage usually due to pressure erosion of an abdominal aortic aneurysm into the third portion of the duodenum. This report describes a case of a 59-year-old man who died of massive gastrointestinal hemorrhage due to a primary aortoduodenal fistula. This case is unique in that the fistula formed as a result of complex atherosclerotic disease of the abdominal aorta, with adventitial chronic inflammation and foreign body reaction against atheromatous plaque, and not from an aneurysm. We were unable to identify any other reports of aortoduodenal fistulas developing spontaneously in the absence of aneurysmal disease of the aorta.