Small bowel obstruction is a common complication after ileal pouch-anal anastomosis. This review of 460 patients examines the frequency of small bowel obstruction and determines potential risk factors. The leading indication for ileal pouch-anal anastomosis was ulcerative colitis (83 percent). In 142 patients (31 percent), loop ileostomy was rotated 180° to facilitate emptying of the ileostomy. Ninety-four patients (20 percent) had 109 episodes of obstruction. Obstruction occurred after creation of the pouch (40 episodes), closure of the ileostomy (29 episodes), or developed during the subsequent followup period (40 episodes). Operative intervention was required in 39 percent of the episodes (7 percent of all patients). At operation, the most common point of obstruction was at closure of the ileostomy (n=22/42, 52 percent). In 16 of these patients, the ileostomy had been rotated. Multiple risk factors, including age, sex, primary diagnosis, surgeon incidence, pouch type, prior colectomy, steroid usage, stomal rotation, technique of closure of the ileostomy, and prior obstruction, were examined by univariate and multivariate analysis. Of all factors, only stomal rotation was statistically significant (P= 0.0005, chi-squared analysis). Rotation of the loop ileostomy during ileal pouch-anal anastomosis, although an apparent technical refinement, is unnecessary and predisposes to obstruction.