Information concerning the natural history of peptic ulcer disease commencing in childhood is limited. We have followed up 19 individuals in whom this diagnosis had been made in childhood 14–27 years previously. Strict diagnostic criteria were used. A high incidence of morbidity persisting into adult life was found. On investigation 9 (47%) had had a proven ulcer since entering adult life. Ten (53%) were no longer prone to recurring abdominal pain, but four of these had undergone vagotomy and pyloroplasty (three after the age of 21) for intractable symptoms. Thus, only six patients (31%) had made a lasting and spontaneous recovery. Serious complications had occurred at some time in the past in 10 cases (53%). Overt gastrointestinal bleeding had occurred in eight (42%), and this had been after the age of 18 years in three. Duodenal perforation occurred in one subject, and severe pyloric stenosis in another, both of whom were aged 21 years. One subject developed a penetrating duodenal ulcer at the age of 24 years. Seven (37%) had undergone surgery, and in two of these cases more than one operation had been performed. Fifty-eight percent of complications suffered and 89% of surgical operations performed involved patients of 21 years or older. These findings firmly reinforce the opinion that the disorder frequently persists into adult life. The impact of modern means of medical therapy, such as the H2 receptor antagonists, has not yet been fully evaluated.