In a patient with episodes of postprandial epigastric pain and fullness, intraluminal duodenal diverticulum was diagnosed preoperatively by roentgenographic study. Cure was obtained by excision of the diverticular wall. The pathogenesis of this disorder is explained by elongation of a partial duodenal diaphragm under the influence of peristalsis. The characteristic roentgenographic finding is an intraluminal barium collection surrounded by a radiolucent halo. Surgical treatment consisted of excision of the diverticular sac. Operations for duodenal diaphragm illustrate the different procedures that may be required by this related disorder.