A disease of the jejunum of an infant girl similar to multifocal colitis cystica is reported and termed enteritis cystica polyposa. It consisted of multiple polypoid lesions which involved primarily the mucosa, but in one instance it also involved the submucosa to the muscularis propria. There were cystic glands and pools of extruded mucin surrounded by a chronic productive inflammation and a hyperplastic disorganized muscularis mucosae. The infant also had congenital cystic disease of the lungs and polycystic kidneys, but an acquired etiology for the jejunal lesions was favored rather than a congenital one on the basis of their similarity to those of colitis cystica, their structural features, and the fact that similar lesions have been produced experimentally.