In paediatrics neuronal intestinal dysplasia (NID) has frequently been described, but in adults the clinical picture was not recognised. NID has been diagnosed in adults as well as children with impaired colonic motility since enzymehistochemical methods became available. Patients with primary chronic constipation (n = 41) and with diverticulosis of the sigmoid colon (n = 23) showed neuronal colonic dysplasia, whereas healthy controls (n = 15) had a normal innervation of the intestinal wall (p < 0.001). The results of this clinical study make a worthwile contribution to the understanding of the aetiology and pathogenesis of primary chronic constipation and diverticulosis of the colon in adults. Conservative treatment is usually unavailing and surgical intervention is needed. Hence, where strictly indicated, resection of the pathologically disturbed colon segment is often the only successful therapeutic procedure.