This article focuses on the relationship between political parties and interest groups in contemporary democracies. Although this is a key topic for assessing the evolution of representative political systems and the quality of democracies, the theoretical and empirical studies have not developed a cumulative body of knowledge. As well as the lack of an integrated perspective, we argue that the literature on this topic has remained conceptually fuzzy and has failed to elaborate a common approach to examine how parties and interest organisations interact. Although some researchers point to a weakening of relations between parties and interest groups, the most current data point not to disappearance but to a change in the way both political actors interact. This article contributes to updating the research on the topic and also sheds light on why the literature has remained segmented. The study shows that the variety of conceptualisations, approaches and typologies has led to incongruent - and often non-comparable - results. The final section identifies a number of research gaps and suggest new topics and approaches that can unify this object of study in the near future.