Small bowel obstruction remains the most common complication after proctocolectomy with ileal pouch-anal anastomosis. Of 626 patients who underwent this operation between January 1981 and October 1986 for ulcerative colitis (544 patients), familial adenomatous polyposis (72 patients), or indeterminate colitis (ten patients), 17% developed small bowel obstruction, 7.5% of whom required surgical intervention. The obstruction occurred either before or after closure of the temporary ileostomy. Patients who had a temporary Brooke ileostomy were more likely to develop obstruction (four of 32 patients, 12.5%) than those who had a loop ileostomy (25 of 564 patients, 4.6%) (p = 0.07). Also, patients who had had previous operations were at greater risk of obstruction (8.5%) than those who had not (2.2%) (p less than 0.04).