&NA;The procedure of choice in the emergency surgical management of ulcerative colitis and Crohn's colitis is often subtotal colectomy and ileostomy. Further surgery of the retained rectum may be delayed, sometimes for many years. The risk of malignant change in ulcerative colitis is well documented; the cancer risk seems to be much less in Crohn's disease. Five cases are reported where carcinoma developed in the out‐of‐circuit rectal stump after subtotal colectomy, three cases of ulcerative colitis, and two of Crohn's disease. The importance of regular surveillance or removal of an excluded rectum is emphasized