The aim of the anti-doping work is to prevent the use of substances and methods that are hazardous for health and/or improve performance, to ensure the right to fair and pure sports and to control the adherence to the ethical principles of sports and medicine. The national anti-doping committees are responsible for doping control of athletes who participate in organized sports. They continually update doping regulations that are based on the regulations of World Anti-Doping Agency (WADA , www.wada-ama.org). This article describes the general principles of anti-doping regulation and provides guidance and examples for some common situations. Whenever there is uncertainty, check the facts at the website of your national anti-doping organization or WADA.