Two cases are presented in which anomalies of the aortic arch system were associated with development of an arterial-esophageal fistula. The fistula resulted in massive upper gastrointestinal hemorrhage and death. In each malformation, part of the anomalous aortic arch system lay against the esophagus and thereby provided the anatomic substrate for an arterial-esophageal fistula. In both cases, nonmassive ("sentinel") hemorrhage occurred prior to the massive fatal hemorrhage. Recognition of the significance of the "sentinel" hemorrhage may allow surgical correction of the problem avoiding uncontrolled massive hemorrhage.