Even though health policy is almost exclusively Member State competence, the last 10-20 years have shown substantial developments with regard to an arising European health policy. These developments cannot the least be attributed to the European Court of Justice (ECJ) who has actively helped shaping European health policy through decisions on case law. Therefore, this book deals with the role of the European Court of Justice in health policy integration by first identifying the extent of it in cross-border healthcare, and second by analyzing why the ECJ has played such a substantial role in this process. In order to do so, three hypotheses have been established on the basis of an extensive literature review and are analyzed by applying five different integration theories on specific case law and related documents. The book adds value to the existing discussion by providing a comprehensive analysis of explicit case judgments and by revealing which of the hypotheses seems most feasible.