Forty-nine cases of duodenal ulcer in children are presented. Strict radiological and clinical criteria were observed in making this diagnosis. The children came from a population of approximately 100,000 children over a 10-year period. Upper abdominal pain was the commonest presenting symptom, and exacerbations and remissions of the disease were observed to be shorter than is expected in the adult. Haemorrhage occurred as a complication in 24% and there were no cases of perforation or stenosis. A family history of duodenal ulcer was found to be highly significant, and it was found that in 55% of patients there was an important element of stress. Treatment was conservative in all but 2 cases, in both of which a vagotomy and pyloroplasty were performed. These operations were judged to have been successful. 6 cases had appendicectomy in the hope of relieving undiagnosed abdominal pain, in which it was unsuccessful. A plea is made for keeping this diagnosis in mind when dealing with abdominal pain in children.