Abstract Background/Purpose: Intestinal neuronal dysplasia (IND) is a complex alteration of the enteric nervous system (ENS) that may involve rectum, colon, or the whole intestine. This disorder is a frequent cause of intestinal dysmotility and pseudo-obstruction in the first 3 years of life. The aim of this study was to identify possible associations and correlations of IND with other gastrointestinal and nongastrointestinal anomalies. Methods: From 1986 to 2000, 95 cases of IND type B without aganglionosis were diagnosed. Fifteen cases were diffuse IND, whereas the remaining 80 were rectocolonic neuronal dysplasia. The diagnosis was performed on rectal suction biopsy specimens taken 2 to 10 cm above the pectinate line. Acetylcholinesterase (AChE), lactic dehydrogenase (LDH), and NADPH-diaphorase (NADPH-d) histochemical techniques were performed on serial cryostatic sections. We used Schärli and Meier-Ruge criteria (1981) for the diagnosis of IND until 1992, when we adopted Borchard et al criteria (1991). A retrospective analysis of the clinical data was performed to identify IND-associated anomalies. Results: These anomalies included anorectal malformations (9 cases), intestinal malrotation (8), megacystis (5), congenital short small bowel (4), hypertrophic pyloric stenosis (3), necrotizing enterocolitis (2), mental retardation (2), short stature (2), facial dysmorphism (2), Down syndrome (1), intestinal atresia (1), diffuse intestinal angiomatosis (1), histiocytosis (1), microvillus agenesia (1), and hearing loss (1). Overall, 43 associated anomalies were found in 29 IND cases (30.5%). Gastrointestinal anomalies accounted for 67.4% (29 of 43 anomalies) of associated disorders. The incidence of associated anomalies was higher in diffuse IND (80% of cases, 12 of 15) than in rectocolonic forms (21.2%, 17 of 80). Conclusions: Unlike Hirschsprung's disease, which is determined genetically, IND pathogenesis is unknown. The analysis of associated anomalies in IND population is an important clinical approach to investigate possible pathogenetic correlations. Two recessive syndromes were identified (3 families). The first was characterized by IND, intestinal malrotation, and congenital short bowel, the second by IND, short stature, mental retardation, and facial dysmorphism. In this study, gastrointestinal anomalies accounted for 67.4% of all associated disorders. These data suggest a strong correlation between IND and intestinal development. Abnormalities of the fetal ENS could determine the IND phenotype, which is likely to contribute to the pathogenesis of different intestinal malformations and in particular of anorectal and “rotation” anomalies. J Pediatr Surg 37:219-223. Copyright © 2002 by W.B. Saunders Company.