People at average risk for colorectal cancer (asymptomatic, age > or = 45 years, no risk factors) are offered fecal occult blood testing each year and sigmoidoscopy every five years. In case of a positive fecal occult blood test, examination of the whole colon by colonoscopy should be performed. Colorectal cancer risk is significantly lowered by endoscopic polypectomy in patients with adenomas. After complete removal of adenomatous polyps a control colonoscopy is advised three years after the initial examination. People with a positive family history of colorectal cancer or adenomatous polyps, of inherited polyposis syndromes, of a hereditary non-polyposis colorectal cancer, after polypectomy, after resection of colorectal cancer and with inflammatory bowel disease possess an increased risk for the development of colorectal cancer. Surveillance recommendations in these cases are detailed. In order to increase the cost-benefit ratio in surveillance after curative resection of colorectal cancer the frequency of the surveillance procedures can be reduced. In patients with total or extensive ulcerative colitis colonoscopy with multiple biopsies should be performed after a disease duration of eight to ten years, further recommendations depend on the histopathologic results.