Cancer that occurs in patients with ulcerative colitis can arise in any portion of the large bowel, and it carries the same prognosis as colon cancer in general. Although the risk of cancer is relatively low in the first decade after the onset of colitis, it increases to approximately 20% each decade thereafter. In addition to duration of disease, the incidence of colon cancer rises with extent of colonic involvement and severity of disease.Because all currently available screening tests (including repetitive biopsies linking dysplasia and bowel mucosa transformation to cancer) are problematic,most patients with this unusually high risk for colon cancer will probably benefit at some point from prophylactic colectomy. The application of molecular markers (e.g., sucrase isomaltase) may more quantitatively define risk for transformation in an individual patient, allowing a more rational recommendation for preemptive surgery.When ileoproctostomy is performed, preserving the distal rectum and anus, a worrisome incidence of carcinoma has still been observed. Proctocolectomy with a Brooke ileostomy or abdominal colectomy, mucosal proctectomy, and ileoanal reconnection with one of the reservoir procedures can be applied to individual patients, which provides complete freedom from subsequent cancer development and the most appropriate bowel function for the patient’s psychological and functional well-being to be chosen.