Thirty-two children with ulcer disease were seen over a four-year period. Twenty-seven children had a primary ulcer and five had an ulcer associated with an acute or chronic illness (secondary ulcer). Antral ulcer was diagnosed most commonly, followed by duodenal ulcer and gastric body ulcer. The ratio of gastric ulcer to duodenal ulcer was 17:11. Diagnosis of ulcer was accomplished by endoscopy in 97% of the patients and by radiography in 70% of those studied. Radiologic accuracy was obtained in 89% with duodenal ulcer but in only 50% of those with gastric ulcer. Children with primary gastric ulcer presented with no evidence of chronicity and 12% had persistence or recurrence of ulcer during follow-up. Eighty-two percent of the children with primary duodenal ulcer presented with chronic symptoms consisting of abdominal pain, nausea, vomiting or recurrent bleeding and 45% had persistence or recurrence of ulcer during follow-up. Children with secondary ulcer all presented with acute symptoms and none had persistence or recurrence. Twenty children were treated prospectively with cimetidine and 11 were treated with antacids. Repeat endoscopy was employed in 16 as a measure of healing. All children with isolated antral ulcer did well clinically, regardless of mode of therapy and of those studied by re-endoscopy all showed complete or substantial healing at six to eight weeks. Treatment of a small group of children with primary duodenal ulcer using cimetidine was initially efficacious, although recurrence of ulcer was noted after cessation of treatment in four of six children given cimetidine. In addition, cimetidine appears to offer no advantage compared to antacids in the treatment of uncomplicated antral ulcer in children.