Thirty-five patients with chronic ulcerative colitis and 30 with Crohn's disease who underwent abdominal colectomy and ileorectostomy in recognition of normal or minimaly involved rectal segments have been observed for from 5 to 18 years. Two patients died in the immediate postoperative period, and 14 died subsequently, two from rectal carcinoma. Of 24 surviving patients who had chronic ulcerative colitis, 17 have intact anastomoses; in seven proctitis developed requiring proctectomy and ileostomy. Young patients required proctectomy most often. Of 25 surviving patients with Crohn's disease, 13 required proctectomy; rectal function is satisfactory in only nine of 12 living with intact anastomoses. Conservation of normal or minimally diseased rectal segments is considered appropriate for patients with Crohn's disease despite a high incidence of subsequent proctitis. Predisposition to rectal neoplasia, however, must temper decisions about ileorectostomy for chronic ulcerative colitis.