Innumerable juvenile polyps were recognised in the stomach of an 18-year-old girl. The clinical and pathological observations of the propositus have been already reported (in "Japanese Journal of Gastroenterology" and "Gastroenterology"). Her elder brother underwent a subtotal gastrectomy because of gastric polyposis at 14 years of age. Supplementary data of their clinical findings are given. They had no extragastric polyps on roentgenographic and endoscopic studies. A classification of this hereditary syndrome as a newly designated entity, juvenile polyposis of the stomach was proposed. Both siblings are now in good health.