Since November 1980, 180 patients underwent abdominal colectomy, rectal mucosectomy, ileoanal reservoir construction, and ileoanal anastomosis at the authors' institutions. One hundred twenty-nine patients had restoration of intestinal continuity before the end of 1986. One hundred fourteen of these patients (88 percent) were available for follow-up at a mean length of time of 5.0 years from ileostomy closure (range, 16 to 88 months). The mean number of pouch evacuations was 5.4 +/- 2.5 during the day (range, 1 to 12) and 1.5 +/- 1.0 at night (range, 0 to 6). Ninety-one percent of patients reported perfect or almost perfect daytime continence, and 74 percent found this true at night. Sixty-three percent of patients believed their pouch function continued to improve over many years. Ninety-five percent of patients questioned would choose an ileoanal reservoir again instead of a permanent ileostomy. This long-term assessment of the function of the ileoanal reservoir confirms that it is a viable, although not perfect, option in the management of ulcerative colitis and familial adenomatous polyposis.