Hypoganglionosis (HG) is regarded as a rare form of neuronal intestinal malformation, which ineludes aganglionosis, neurona1 intestinal dysplasia type A (NID type A), 8 (NID type B) or combined type. Although most common symptom is chronic constipation, ileus is sometimes met with wide extent of lesion in pediatric patients. Preoperative diagnosis can be made by combination of colon transit time study, anal manometry, defecography and/or rectal biopsy in addition to intractable symptom. We exenced two cases of adult type HG, One is assumed to be a congenital type, while the other is assumed to be an acquired type. They were treated with total colectomy and ileorectal anastomosis without sequelae. Both patients have showed normal bowel habit in twenty four months and seven months after operation. (Kor J Gastroenterol 1998;32:261-266)