International cooperation has developed rapidly on a wide range of policy areas in the last decades. National governments have learned to look across national borders in order to improve their policy systems, as in the case of health care, the subject of this book. There is a need to compare policy results, and therefore international comparison of statistical data is of great importance. For decades, international organisations like OECD and WHO have collected and distributed statistical information of member states in order to describe developments within these countries. However, comparability across countries has always been problematic. The task of international comparison of statistical data has only reluctantly been adopted due to difficulties caused by differences in definition and methods of data collection. In this book a method is presented for the advancement of international comparison of health care. Starting points are the determination of the boundaries of national health care systems and the activities that take place within these boundaries. This book is meant for all those working in the international health care field or interested in international comparison, who want to be aware of the pitfalls of international comparison and who want to learn, from the described experiences, how to solve problems of comparability.