We describe a form of intractable diarrhea in six children (four girls) with similar clinical histories and identical histopathologic features. The children had watery diarrhea of neonatal onset requiring total parenteral nutrition. Two had siblings who had died of diarrhea in the first year of life; two others are sisters. Repeated duodenal or jejunal biopsies revealed villous atrophy with normal or hyperplastic and regenerative cryptae, normal cellularity of the lamina mesenterii propria, and no signs of T-cell activation. The main histologic features are epithelial dysplasia with focal crowding and disorganization of the surface enterocytes, pseudocystic formation of the glands, and abnormal regenerative cryptae. The basement membrane components were studied with polyclonal antibodies on frozen specimens, and were compared with biopsy specimens from patients with celiac disease or autoimmune enteropathy. Relative to the control subjects, there was faint and irregular deposition of laminin at the epithelium-lamina mesenterii propria interface, whereas deposits of heparan sulfate proteoglycan were large and lamellar. The primary or secondary nature of these modifications of the basement membrane remains to be determined, but the modifications might be related to epithelial abnormalities and to the severity of this neonatal diarrhea, which resisted all treatment and necessitated permanent total parenteral nutrition.