One hundred consecutive patients treated by restorative proctocolectomy with construction of an ileo-anal anastomosis and a J-shaped (n = 90) or an S-shaped ileal reservoir were studied prospectively to evaluate postoperative complications and functional outcome and to search for factors that might influence results. There were no deaths. Postoperative complications requiring surgery were pelvic sepsis (3 patients), pouch-related fistula (2), peritonitis following ileostomy closure (3) and small bowel obstruction (6), with an overall relaparotomy rate of 14%. The cumulative risk of pouchitis was 30% at 2 years. The average stool frequency decreased gradually, stabilizing at about five evacuations/24 h after 1 year. At that time 9% of patients still had greater than or equal to 7 day-time evacuations and 40% had night evacuations (greater than 1/week). These parameters did not improve further with time. Mucous soiling, a frequent problem initially, also diminished with time, occurring in 30% of patients at 1 year. At 2 years, however, this mucous leak occurred in only 20%, suggesting that improvement of continence can be expected to occur even beyond one year. Despite defects in function patient satisfaction was generally excellent. So far only three patients have preferred conversion to an ileostomy. To establish which factors might influence the functional results a specially designed scoring system, combining all functional variables, was used. It was shown that results deteriorated with increasing age and that elderly women tended to have a poorer result than elderly men. Sex, previous parity or postoperative complications appeared not to affect the functional outcome. Male sexual disturbances occurred in 8%.(ABSTRACT TRUNCATED AT 250 WORDS)