Aneurysms of the thoracic aorta simulated primary esophageal disease both clinically and radiographically in 5 patients. Four had an aortoesophageal fistula at the time of presentation; endoscopic biopsy of a presumed esophageal tumor precipitated hematemesis in the fifth patient. In retrospect, the fistulas were demonstrated by barium esophagography in 3 patients. In 3, arteriography showed the aortic aneurysm but failed to reveal the fistula. The literature confirms a similar presentation for most other aortoesophageal fistulas, with premonitory esophageal bleeding followed hours to days later by massive hemorrhage. Of the reported cases of rupture of aneurysms of the thoracic aorta, 12% bled into the esophagus. While clinical and radiographic distinction between primary esophageal disease and esophageal manifestations of an aortic aneurysm is occasionally difficult, it is crucial for proper management.