Although the debate over whether to criminalize anti-cartel enforcement is still building around the world, there is a strong case in its favor. We use the term “cartel” to refer to the particular types of horizontal collusion that would be subjected to criminal sanctions in criminal-law jurisdictions, namely the most unambiguous (“naked”) and socially harmful (“hard-core”) forms of price /xing, bid-rigging, and market allocation.1 In our view, criminalization is a policy that re0ects pragmatic governmental intervention in economic systems characterized by heavy reliance on free markets.2 1is policy is based on experience and reason and is supported by moral considerations. We explain general harms of cartels, summarize the empirical evidence to date on the frequency and seriousness of the cartel problem, discuss the extent to which criminalization draws on universal moral concerns, and discuss pragmatic considerations of criminalization’s e2ectiveness in deterring cartels.