This thesis gives a review of the world system of the fight against the doping in sport. It presents the institutions in charge of the antidoping fight, rules that apply and the procedure. System of the antidoping fight in the world is based on the wide consensus and coordination of various public authorities, governments and sport organizations. At the beginning, the concept of doping is approached from the philosophical and ethical side. Two opposing perspectives are described. Following is the historical overview of doping and the development of fight against doping. In the central part of the thesis the rules of the World Anti-Doping Agency are studied. The fundamental source of the antidoping rules is the World Anti-Doping Code. Among other things it contains: definition of doping, proof of doping, sanctions, appeals, testing and education. The antidoping system of Croatia is presented next. The rules and the legislature are in accordance with the Code. The thesis finishes with the review of the practice of the Court of Arbitration for Sport. As the independent body charged with resolving disputes in sport, including doping, it’s bound to secure an efficient and righteous procedure for everyone. Therefore, the rules of procedure will be shown first and then a couple of actual cases.