Intraluminal duodenal diverticulum and incomplete congenital duodenal diaphragm are unusual and have been considered separate entities. Anatomical variations in 9 children with symptoms of duodenal obstruction or bleeding ranged from a tight transverse diaphragm to a prolapsing diaphragm identical to the intraluminal diverticulum. Congenital duodenal diaphragm and intraluminal duodenal diverticulum are probably different forms of an obstructing congenital duodenal membrane. The clinical and roentgen features of this anomaly are discussed.