Colorecal cancer undergo relatively long preneoplastic processes before being invasive. Fecal occult blood test (FOBT) has been a useful tool to detect the advanced colorectal cancers with cost-effectiveness. However, the patient's compliance to FOBT was poor because of low sensitivity and annual sampling. The sigmoidoscopy and colonoscopy have the ten-year preventive effect for the advanced cancer. Recently the DNA stool test for detection of mutations has showed excellent sensitivity and specificity. It has several adventages such as collection of samples and automated analysis. Virtual colonoscopy, especially CT colonograpy, can be a viable option for the colorecal cancer screening. In November 2001, the Korean Society of Coloproctology (KSCP) and the Natinal Cancer Center (NCC) developed the guidelines on screening and surveillance for early detection of colorectal cancers in Korea. Average-risk men and women should start colonoscopic examination with a 10-year interval at the age of 50. Individuals with increased risk such as those with a family or personal history of colorectal cancer or colorectal adenomas, or family history of familial adenomatous polyposis, hereditary non-polyposis colorectal cancer should consult their surveillance to the specialty-physicians. The ideal screening tools may change by age.