Six patients with polyposis coli and five with chronic ulcerative colitis underwent total colectomy and mucosal proctectomy with preservation of the anal sphincter and levator ani muscle. An ileal reservoir, constructed from the terminal ileum, is brought out through the anal sphincter for anastomosis to to the anus at the dentate line. Two patients in the series had a three-limb reservoir with anastomosis of a short efferent ileal limb to the anus (Parks technique). Nine patients had a two-limb J-shaped reservoir with the apex of the reservoir anastomosed to the anus (Utsunomiya technique). All patients had a temporary defunctioning ileostomy. There were no deaths. Two patients suffered from severe infection within the rectal muscle cuff. One resolved completely with spontaneous drainage into the reservoir; the other had continuing sepsis and eventually required excision of the anus and conversion to a continent ileostomy. All patients remain in good general condition with no disturbance of urinary or sexual function. Continence is satisfactory in all patients but two wear a pad at night. All evacuate their reservoirs spontaneously: none requires the use of a catheter. For most patients stool frequency varies from four to eight times daily but two patients have more frequent bowel motions. Colitis patients have more frequent bowel activity than those with polyposis. Three patients take Imodium tablets to lessen bowel frequency. The operation should be reserved for specialized centres and is still under trial; however, it appears likely to become the operation of choice for all patients with polyposis coli and for many patients with chronic ulcerative colitis.