With the odd exception (Wallace, 2000), the term `Europeanisation¿ has come to be used in reference to the impact of the European Union (EU) across member states (Bulmer and Burch, 1998). Assessing the nature of this impact is, however, extremely problematic. The EU does not present a single over-arching `European principle of organization¿ that we might examine for evidence of its influence. Analysis of change within European states also runs into the problem of separating out `Europeanisation¿ from other equally plausible variables. Finally, assuming that these difficulties can be overcome, there remains the methodological problem of how to compare the impact of the EU and/or Europeanisation in quite differently constituted national state forms. The point of this article is to try to elucidate a framework that avoids these problems. Taking the focus of analysis to the meso level, the policy networks approach is utilised to provide comparative characterizations of cross-national policy-making processes, supported by a theory of political integration to explain variation and change in alternative national policies arising as a consequence of Europeanisation. The article concludes by deploying a number of propositions from neofunctionalism in order to provide precise expectations about the effects of political integration on the institutional and political organisation of member states. © 2002, Sage Publications. All rights reserved.