Drugs may be used by athletes for a number of reasons, including performance enhancement. The role of the World Anti-Doping Agency (WADA) is vital to ensure a winning performance has been achieved by fair means. Substances and methods that are included on the WADA Prohibited List are described. The procedures for testing banned substances are explained, together with the sanctions that are applied in doping cases. The extent of drug misuse in sport is discussed together with consideration of why drugs are used for performance enhancement. (Contains 5 boxes, 2 tables, 1 figure, and 5 online resources.)