Until today, it is relatively disputed how European integration impacts on domestic associations and the patterns of public-private interactions at the national level. While some predict a withering away of national corporatisms, others predict they would be reinforced. By making organization theory available to institution-theoretical approaches, the paper offers a conceptual means that makes it possible to present an encompassing and theory-guided picture of the impact of European integration on societal structures in the member states. Associations - in the presented cases, business associations of the transport sector in Germany and the Netherlands -, as intermediate organisations operate at the interface between private and public actors and incorporate the dynamics of their political and economic environments in both structural and strategic terms. It is argued that the way in which the configuration of associations within a sector changes in the course of European integration relates to efforts at this intermediate level to maintain or increase its relative autonomy from both its constituencies and its interlocutors.