Aortoesophageal fistula (AEF) is a rare but frequently lethal cause of upper gastrointestinal bleeding. This is a report of the authors' experience with four cases--two from congenital and two from acquired causes. A review of the pediatric cases reported in the literature is included. The mortality from AEF is high, and can be decreased in two ways. AEF can be prevented by avoiding prolonged nasogastric intubation in patients with known vascular rings, and by promptly removing esophageal foreign bodies and promptly treating periesophageal abscesses. Once an AEF occurs, it presents with typical large-herald upper gastrointestinal bleeding of bright red blood, and cardiovascular collapse. Recognition of this pattern, with vigorous resuscitation and aggressive surgical management, will improve the survival rate.