Preservation of the rectum in chronic ulcerative colitis or familial polyposis conserves continence at the risk of recurrent disease or malignant change. Replacement of rectal mucosa with a graft of ileum in these benign colonic mucosal diseases conserves fecal continence without the threat of continuing disease or the development of carcinoma. Rectal mucosal replacement with construction of a rectal reservoir includes total colectomy, removal of the rectal mucosa-submucosa and its replacement with an ileal graft. A rectal reservoir is constructed when intestinal continuity is restored. Twenty-nine patients have undergone rectal mucosal replacement; 12 for familial polyposis and 17 for ulcerative colitis. Twenty-five patients have had intestinal continuity restored. Patients have been followed from three months to seven years after the restoration of intestinal continuity. Twenty-three patients have a satisfactory result. Fecal continence has been preserved. Patients pass an average of six stools in a 24 hour period.