Antitrust authorities must decide whether and how to consider the national identities of firms. Authorities may follow a neutral enforcement approach or focus on either foreign or domestic firms. We investigate these issues in the context of cartel enforcement against EU, US, and rest-of-the-world (ROW) firms by the European Union and the United States—the two jurisdictions with the longest and most robust enforcement histories. Our results suggest a mix of behaviors. The European Union is more likely to fine domestic and ROW firms than US firms, and the United States is no more likely to fine EU firms than domestic firms but disproportionately targets ROW firms. With respect to the size of fines, EU enforcement outcomes show no significant differences among categories of firms. The United States, however, levies significantly higher fines on foreign firms than domestic firms, whether from the European Union or the rest of the world.