Comparable histologic alterations of intramural nervous tissue were reported in various diseases of the small and large intestine. In 6 cases, an intestinal obstruction was present which led to secondary intramural inflammation. The obstruction was induced by the spastic segment in Hirschsprung's disease (3 cases), by rectal atresia (2 cases) and by postoperative ischemic damage to the intestinal wall (1 case). In 4 other patients, the inflammation was predominant. The diseases considered were necrotizing enterocolitis (1 case), membranous enteritis (1 case) and Crohn's disease (2 cases). On the one hand, inflammatory infiltration composed primarily of lymphocytes was observed histologically in various degrees proximal to the obstruction in all cases. On the other, comparable alterations were found in splittering of nerve fibers and deterioration of nerve cells (degenerative alterations) in the plexus myentericus as well as hyperplasia and hyperchromasia of ganglion cells. Schwann cell proliferation and fibrosis in nerve fibers (reactive alterations). Until now such alterations were only observed in Chagas' disease and in ulcerative colitis, especially complicated by toxic megacolon. It is suspected that the neurodegenerative alterations in these diseases are toxically induced.