In the past 25 years, leniency programs have been established in more than 80 jurisdictions across the globe. The overall purpose of such programs is to create incentives for cartelists to “blow the whistle” and to fully cooperate with the authorities to uncover and sanction the cartel. Leniency programs are a very important tool in the fight against cartels. However, such programs have currently come under pressure from various directions. This article aims to give a practitioners’ overview of the EU Leniency Program, to trace recent challenges, and to highlight current efforts to solve these issues, as well as to provide a practical outlook on the factors to take into account when considering a leniency application.