The outcome of mucosal proctectomy with ileoanal anastomosis in patients with polyposis coli has not been well studied. A series of 25 patients with polyposis treated at the Mount Sinai Hospital over a period of ten years is reported. The mean age of the patients was 23 years. Early postoperative complications were present in seven patients and consisted of thrombophlebitis (three), pelvic sepsis (three), and retraction of the anastomosis (one). Intestinal obstruction requiring laparotomy occurred in another five patients. Twenty-three patients were followed for a mean of 47 months after closure of the ileostomy. Ninety-one percent are satisfied with the operative results. The mean number of bowel movements per 24 hours is 6.0. All patients are continent, but eight have occasional episodes of rectal seepage at night. Nearly 50 percent require some antidiarrheal medication. New adenomatous polyps have developed just above the dentate line in four patients. Patients with polyposis coli seem to have fewer serious complications requiring excision of the ileoanal anastomosis than patients with ulcerative colitis. They also should have lifelong surveillance of the entire gastrointestinal tract even after total colectomy with ileoanal anastomosis.