Because patients with longstanding ulcerative colitis are at an increased risk for developing colorectal cancer, surveillance colonoscopy and colectomy for dysplasia or asymptomatic cancer is advised as a method of reducing cancer-related mortality. Generally, the use of dysplasia as a criterion for a positive test in cancer surveillance has performed poorly. The emerging field of colon cancer genetics has identified several important tumor markers that have the potential to improve sensitivity for the detection of early neoplasia. Specifically, p53 tumor suppressor gene mutations, aneuploidy, and mucin-associated sialosyl-Tn expression appear most promising for future use in surveillance programs.