Four patients with long-standing symptomatic ulcerative colitis confined to the left colon and rectum were treated by resection, mucosal proctectomy and colo-anal sleeve anastomosis. There was no operative mortality or anastomotic leakage. Follow-up has ranged from 12 to 66 months (mean 52 months). Loose bowel motions with urgency and frequency of defaecation were troublesome postoperative symptoms. Recurrence of the colitis in the neorectum with extension into the proximal colon occurred in all patients within 3 to 11 months (mean 6 months) of operation. This necessitated total proctocolectomy with ileostomy in three patients (mean 18 months postoperatively). In the fourth patient the recurrence is medically controlled without a stoma more than 5 years after operation. This operation is unsuitable for the treatment of segmental ulcerative proctocolitis.