Double pylorus is either a congenital abnormality or an acquired complication of peptic ulcer disease. We had followed two patients for 3 and 5 yr, respectively, to observe the processes of formation and the prognosis of double pylorus. Initially, duodenal ulcer was found in one patient with diabetes mellitus and chronic renal failure, and gastric ulcer was found in the other with chronic obstructive pulmonary disease. Both developed double pylorus with refractory courses. In spite of intensive medical treatment, both of them had persistent ulcers in the fistulous tract and failed to develop reepithelization. Helicobacter pylori was found in all of the specimens of gastroduodenal biopsies in both cases. Therefore, we believe that the refractory courses of double pylorus may be related to the underlying diseases and/or the presence of H. pylori. Antibacterial treatment of H. pylori or surgical intervention should be considered for patients with this condition.