This article systematically investigates interest group–party interactions in the Netherlands, Denmark and the United Kingdom based on cross-national surveys with responses from 1,225 interest groups. The findings show that interest groups and parties still interact in the beginning of the twenty-first century, but that the vast majority of their interaction involves a low degree of institutionalisation. Using fractional logit analysis, it is demonstrated that the strength of interest group–party linkage is primarily affected by systematic differences in state–society structures and organisational group characteristics. Moreover, differences are found in what conditions different types of interaction. Whereas historical legacies and partisan origin influence an interest group's structural party links, group resources make interactions of a less institutionalised, ad hoc nature more likely.