Endoanal mucosal proctectomy with preservation of the anal sphincters has been employed as an alternative to the traditional method of rectal excision in 23 patients with ulcerative colitis or Crohn's disease. Ten patients in whom the anal canal was left open and drained had uneventful postoperative courses. Of the remaining 13 patients in whom the top of the anal remnant was oversewn, four had local pelvic sepsis that resolved in a few weeks' time and one patient had a pelvic hematoma requiring relaparotomy and sphincter muscle excision. Postoperative disturbances in bladder or sexual function did not occur in any of the patients. At the latest follow-up (mean 21 months), all patients were fully satisfied with the result of the operation. On proctoscopic examination, an anal remnant, measuring approximately 3 cm from the anal verge, could be demonstrated. Its upper end had healed with a fibrous scar in 50 percent of the patients, whereas a small area of friable granulation tissue, sometimes with a short sinus tract was still observed in the others. The persistence of such lesions was associated with minor mucous discharge occasionally escaping from the anal canal. Biopsies disclosed regeneration of cylindric and transitional types of epithelium. The fate of these epithelial remnants remains to be seen. Endoanal mucosal proctectomy appears to be an attractive alternative to the conventional technique. It prevents a great deal of morbidity and enhances postoperative rehabilitation.