To the extent that European integration results in the decline in the importance of the nation-state as the exclusive seat of formal political power, we can expect attendant changes in those forms of interest aggregation and articulation historically linked to the state. This article suggests that a polity characterised by multi-level governance is emerging in Europe and that this poses a set of new constraints and opportunities for groups that wish to influence political decisions. We argue that group strategy in response to this is a function of: (1) the structure of political opportunities facing a group in the EU; and (2) inherited institutions and ideologies that constrain the capacity of a group to exploit those opportunities. We use this framework to analyse the effect of European integration on four groups: the labour movement, regional movements, the environmental movement and the anti-nuclear movement.