The origin and relevance of substances been identified as Substances of Abuse by the World Anti-Doping Code to establish a levelled playing field in sport, drugs with the potential to enhance performance have to be banned. However, certain substances with the potential to enhance performance are frequently used in a social context unrelated to sports competition, but still result in an anti-doping rule violation. Therefore, in 2021, the World Anti-Doping Agency introduced a new category of substances that initially includes a small number of very specific substances, as well as corresponding rules for how cases should be resolved if an athlete tests positive for one of those substances. The relevance and its limitation of this new category will be analysed in this book.