In developed countries colorectal cancer (CRC) is the second most frequent organ malignancy of both genders. According to the world statistics Czech Republic occupies the top position in incidence of this disease. Approximately 75% of all CRC are the sporadic CRC in subjects with negative family or personal history of the disease. The low (average) risk factor in these subjects is age over 50 years, from which the incidence of CRC nearly doubles in each decade. The following options of screening are available for these subjects: 1. faecal occult blood test (FOBT), 2. flexible sigmoidoscopy, 3. combination of both previous procedures, 4. colonoscopy, 5. virtual colonography. FOBT is the mostly used programme in asymptomatic subjects over age 50 at one-year or at least two-years intervals. In FOBT-positive persons colonoscopy is considered the optimal diagnostic and in the case of polyps also therapeutic method. Prospective randomized studies proving a decrease of CRC-mortality in the range of 15-33% are available only for this type of programme. Screening of sporadic CRC was introduced on national basis in Federal Republic Germany in 1977 and in Czech Republic since the second half of the year 2000. With so many people dying of the disease, we cannot afford not to do its screening.

Keywords: Colonoscopy; Colorectal Neoplasms /diagnosis/; Humans; Occult Blood; Sigmoidoscopy