Many surgeons consider the ileoanal pouch procedure to be the procedure of choice for patients who require surgery for ulcerative colitis and familial adenomatous polyposis. To determine long-term results, 460 patients (mean +/- SD age, 31 +/- 9 years) who underwent the ileoanal pouch procedure from 1980 through 1991 were prospectively observed by computerized registry. The leading indication for operation was ulcerative colitis (n = 382; 83%). A J-shaped reservoir was created in 434 patients (94%). More than 5 years after ileostomy closure, the mean number of bowel movements was 5.8 +/- 2.2, and 13% of patients had leakage. Most patients (94%) were satisfied with their results. Sixteen patients (3.5%) required recreation of a permanent stoma for pouch failure. Complications (major and minor) occurred in 266 patients (58%) and included obstruction (n = 94; 20%), pouch fistula (n = 26; 6%), anastomotic stricture (n = 40; 9%), anastomosis separation (n = 14; 3%), and pouchitis (n = 83; 18%). Modifications in technique and increased operative experience have significantly decreased the incidence of obstruction (P = .05) and pouch-related complications (P = .004). Despite complications, long-term results are acceptable, and patient satisfaction remains high.