This is a detailed exploration of how national political parties have responded to the increasing relevance of European governance. The Europeanization of National Political Parties is the first empirical study to examine the effects of the European Union on the internal organizational dynamics of national political parties. It draws on the results of a major, cross-national project and is based on documentary analysis and some 150 interviews with senior party actors in six EU member states: Austria, Britain, France, Germany, Spain and Sweden. Situated in the context of the debate on Europeanization, the contributors illustrate that national political parties have been surprisingly well equipped to handle the challenges of the increasing importance of multi-level governance in Europe. Following a rigorous analytical framework, the country studies examine thirty relevant political parties and systematically address a clearly defined set of empirical questions. The volume ends with two comparative chapters that analyze the findings from a cross-national perspective and that offer theoretical insights into the problems of party government amid increasing European integration. This text will appeal to all those researching in the fields of European studies, political science and comparative politics.