Countries in virtually every region of the world are criminalizing cartel offenses. Many have initiated prosecutions, several have secured convictions, and a few have imposed jail time. Yet outside the United States the enforcement record is hardly uniform, and the debate about cartel criminalization is far from resolved. This situation raises a host of questions. What spurred the trend toward cartel criminalization? Have the changes been driven primarily by criminalization evangelists such as the United States Department of Justice, whether working bilaterally or through transnational networks? Are organic, bottom-up, national processes also at work, suggesting changing moral sensibilities regarding cartel conduct? To what extent have formal legal changes been accompanied by enhanced enforcement? This Chapter tackles these questions through a review of criminalization and enforcement developments in the United States, Europe, and around the world. While the emerging legal landscape of anti-cartel activity is complex and varies significantly by jurisdiction, the clear trend is toward increased criminalization, as well as more robust enforcement, including collaboration among national antitrust authorities through informal transgovernmental networks. The trends, however, are not uniform, and the implementation of formal legal changes is an open question in light of divergent institutional contexts and social attitudes regarding cartels.