In this "Current Practice in Pediatric Pathology" article, 2 experts in the field and an associate editor of Pediatric and Developmental Pathology discuss the definition, diagnosis, clinical significance, and management of intestinal neuronal dysplasia type B. Intestinal neuronal dysplasia type B has constituted a diagnostic challenge ever since its first description more than 30 years ago. Intestinal neuronal dysplasia type B is regarded by many as a subtle malformation of the enteric nervous system that is limited to the submucosal plexus of the colon. The precise etiology remains unknown, and, to date, no specific diagnostic test exists other than morphology. Over time, with increasing experience, obligate pathological features have been adapted and refined, leading to contemporary diagnostic criteria that are enunciated in this review and placed into context with prior published data. Rigorous application of these criteria, under standardized laboratory conditions, is crucial for accurate diagnosis and future advances in this field.