Surgical treatment of familial adenomatous polyposis (FAP) is still controversial. From 1984 we carried out a prospective evaluation of total colectomy with ileorectal anastomosis (IRA) and restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) to determine differences in postoperative complications, functional results, occurrence of desmoids, and recurrence of polyps in the rectal stump. IRA was performed below the peritoneal reflection and was indicated in the absence of rectal cancer and in the presence of fewer than 10 polyps or minute polyposis in the last 10 cm of the rectal mucosa. IRA patients underwent a regular endoscopic follow-up and prolonged sulindac administration (100 mg twice daily). When criteria for IRA were absent, IPAA was performed adopting a manual anastomosis at the pectinate line. Fourteen patients were operated with IRA and 24 with IPAA. There was no difference in sex and age between the two groups of patients. The number of rectal polyps was significantly different in the two groups. Immediate postoperative complications were observed in only five IPAA patients, three of whom (12%) required reoperation. Late postoperative complications occurred more frequently in IRA patients (14%) than in IPAA patients (4%). Desmoids developed in both groups (five in the IRA group and four in IPAA group). The number of bowel movements was similar in both groups, but 25% of IPAA patients complained of nocturnal fecal soiling. Fulguration or polypectomy for recurrent polyps was necessary in all but two IRA patients at follow-up. The rectal stump was easily eradicated by polyps in all but four patients with minute polyps at surgery. In the latter patients a diffuse or carpeting rectal polyposis occurred. IPAA can give optimum control of colorectal polyposis in FAP patients with an acceptable incidence of postoperative complications and satisfactory functional results. This type of surgical procedure is indicated in most FAP patients, and IRA should be reserved for patients without polyps or with fewer than 10 polyps in the rectal stump; otherwise growth of polyps cannot be adequately controlled.