This contribution reviews what we know about the effectiveness of leniency or amnesty programs in cartel prosecutions. Leniency programs have gradually been adopted by as many as 53 competition policy jurisdictions around the globe during the last 25 years. We show that the available evidence supports that the leniency programs have had a strong impact on anti-cartel policy design and effectiveness. The introduction of leniency programs has offered in most jurisdictions a short-term impact in the discovery of existing cartels, but in the long-term the number of discovered cartels faded down. This is not because cartels become more secretive and remained under cover, but otherwise we show that after leniency is introduced, a strong destabilization and dissuasive effects prevail.