Do the judges of the Court of Justice of the European Union (ECJ) and the US Supreme Court communicate with each other and, if so, what does this communication consist of? This question has become pertinent in the globalised legal context, where legal systems and actors within these legal systems are increasingly interconnected. These interconnections have brought an increasing number of cases with international or foreign aspects to the courts on both sides of the Atlantic Ocean. Moreover, systemic changes, such as the development of the legal order of the European Union (EU) and the increase in the number of international legal instruments, have obliged the courts to develop expertise concerning the application of legal sources elaborated outside of their national legal systems. At the same time, meetings in transnational judicial networks and the availability of foreign legal sources, for example through internet databases, have made it easier and natural for judges to take an interest in developments outside of their national borders. Starting from these observations, this chapter explores the relations between the highest courts in the USA and in Europe, and the impact of these relations on judicial decision-making in the US and European legal orders. What kind of contacts exist between the US Supreme Court and the ECJ, and how do these contacts influence judicial decision-making in the US and EU legal orders? This central research question can be divided in several sub-questions: what examples of transatlantic communication can be identified in the relations between the US Supreme Court and the ECJ? What motives do the two courts have for engaging in this communication? Does the communication between the courts constitute a real 'dialogue', involving an aspect of deliberation? To what extent does this communication have an influence on the decision-making of the courts?