Between 1996 and 2002, 22 cases of Hirschsprung's disease were treated laparoscopically by endorectal pull-through operation. The proximal margin of the resected bowel materials from these 22 patients were examined histologically by frozen sections at surgery and also after surgery using H&E staining, and complete resection of the aganglionic segment was confirmed. Eleven patients, in whom an informed consent was obtained at randomly, underwent suction biopsy from the pulled-though neorectum after surgery. Of these 11 patients, 2 revealed many AchE-positive nerve fibers in the lamina propria, the muscularis mucosa and around the ganglion cells in the submucosal plexuses. These structural changes were similar to intestinal neuronal dysplasia that was characterized by hyperganglionosis and other neuronal abnormalities. The remaining 9 revealed no AchE activity. Unexpectedly, the two patients showing AchE activity in their neorectum continued to have persistent constipation and were treated with laxatives or glycerin enema. It was suggested that their persistent constipation was caused by intestinal neuronal dysplasia showing an abnormal increase of AchE activity in spite of presence of ganglion cells of the neorectum after surgery, but it was uncertain that they were primary condition as a HaIND or secondary reactions after surgery.