The reported risk of small-bowel obstruction (SBO) after major abdominal surgery varies. The aim of this study was to study frequency and risk factors of SBO after ileal pouch-anal anastomosis for ulcerative colitis. Review of the medical records of 188 patients operated with restorative proctocolectomy between 1985 and 1997. All admissions to the hospital were registered and symptoms and X-ray findings consistent with ileus were analysed in relation to preoperative and operative data. SBO was the dominating cause of hospitalization. Forty-eight patients (25.5%) had developed SBO after a median of 76 (range 6-196) months of follow-up, of whom 26 were operated on. The cause of obstruction was adhesion in all but one patient. Early obstruction events were common and accounted for 27% of all operations. Twenty-five of 26 patients who were operated on had a diverting loop-ileostomy compared to 111/162 in the not-operated-on group (p < 0.01). In total, 696 days were spent at the hospital because of SBO. SBO is common following pouch surgery and is the dominating cause of hospitalization postoperatively. About 25% of patients developed SBO and half of them needed surgery. The use of a diverting loop-ileostomy was related to an increased risk of surgery for SBO.