The patterns of interaction between state and business are conditional upon the structure of the EU multilevel system. So far, I have accounted for these patterns by general references to the transformation of the state in capitalist democracies and to the dynamics of socio-economic sub-systems. To advance a more detailed explanation of the EU impact on domestic interest organizations and modes of interest intermediation, I draw on the Europeanization concept that has come to guide the analysis of the EU consequences for its member states in recent years. An important analytical tool often linked to this concept is the so-called degree of fit (Knill and Lenschow 1998; Cowles, Caporaso and Risse 2001) among the EU and its member states. This concept is supposed to explain a large part of the national adaptation to European integration. After discussing this concept, I also put competing propositions about the EU impact on domestic interest intermediation and domestic interest groups to the test.