Ten patients (5 male, 5 female, mean age: 29.4 years) with tuberous sclerosis were investigated for gastrointestinal polyps. Three had adenomatous colonic polyps, one had a single duodenal hamartomatous polyp and the fifth a hyperplastic gastric polyp. This high prevalence (50%) should put the gastro-intestinal investigation as a useful test in the diagnosis of tuberous sclerosis, particularly in the incomplete varieties of disease. Conversely, tuberous sclerosis should be considered in the differential diagnosis of digestive polyposis.