Gastroesophageal reflux has rarely been reported in the Zollinger-Ellison syndrome, presumably due to elevation in the lower esophageal sphincter pressure. We have evaluated 15 patients with the Zollinger-Ellison syndrome for evidence of esophageal disease. Five presented initially with esophageal disease: one, reflux symptoms; two, severe esophagitis; and two, strictures. Six of 15 had heartburn and nine of 15, objective evidence for reflux disease. Mean lower esophageal sphincter pressure was higher in the Zollinger-Ellison syndrome than in controls but was unrelated to serum gastrin levels. Zollinger-Ellison syndrome patients without heartburn had a higher mean sphincter pressure than did patients with heartburn (who had a mean sphincter pressure similar to that of controls but greater than that in patients with idiopathic gastroesophageal reflux). Four patients had biopsy evidence of esophagitis, one in association with Barrett's epithelium. Gastroesophageal reflux and its complications appear to be common in the Zollinger-Ellison syndrome.