The chapter analyses the intersection of competition law enforcement and criminal justice. It sets out the primary theoretical justification for criminal cartel sanctions: (economic) deterrence. Supporters of antitrust criminalisation usually argue that the optimally deterrent cartel fine is too large to be imposed and that a global trend towards criminalisation of cartel activity can be detected at present. What was once primarily a US phenomenon has become international, with countries as diverse as Israel, Brazil and Australia pursuing a policy of cartel criminalisation. This chapter evaluates some of the inherent practical problems with criminal cartel sanctions. It provides insights into how best to ensure that cartel criminalisation improves the effectiveness of a criminalised regime’s competition policy. The chapter comprises two substantive sections. The first outlines the deterrence-based theoretical justification for criminal cartel sanctions. The second critically analyses two important inherent problems that arise when criminal sanctions are used to deter cartel activity: the difficulty of securing efficient competition law enforcement when criminal cartel sanctions are employed; and the need to connect the criminalised cartel activity to morally wrongful behaviour.