Primary prevention - reduction of risk of developing of a tumor. It is a question of our influence(general practitioners) on the life style of our patients, but also an in-depth knowledge of the history of their families. Secondary prevention - early identification of oncological diseases. Slovakia has followed the example of the Czech Republic and prepared a national screening programme of colorectal cancer as of June 2001. There was an information campaign for general practitioners and the public and the project has been launched in January 2002. The current statistics indicates that a general practitioner can identify 1-2 cases of advanced colorectal cancer annually. We can prevent such a development in case of our patients. A general practitioner should carry out routinely an examination per rectum and test stools for occult bleeding once per two years during a preventive check-up of patients over 50. This simple, but systematically carried out proceeding can bring results.