An unselected series of patients with chronic ulcerative colitis from a defined catchment area underwent endoscopic and histologic cancer surveillance from 1977 to 1985. At the end point of the study, which included a total of 93 patients, there were 38 patients with total colitis of more than 10 years' duration. There was one case of colonic carcinoma, two cases of high-grade dysplasia, and no death due to colorectal cancer. We conclude that in an unselected group of patients with ulcerative colitis, the risk for colorectal dysplasia and cancer is low and that a surveillance program is reliable and can be performed at a community hospital.