The purpose of this seminar is to gain an in-depth knowledge about the contemporary political science literature on interest group politics in liberal democracies. More in particular, we will discuss the following important puzzles. First, who mobilizes for collective action: Why are some interests, like consumers or the unemployed, so hard to mobilize and others, like farmers or IT-firms, more successful in getting organized? A second puzzle concerns influence: Under which conditions do interest groups achieve their political objectives? Is this a matter of strategies, resources, experience or networks? The third theme concerns the relation between interests groups and their broader environment. How do organizational patterns differ from country to country? And what is the relation between interest groups and other key political actors such as political parties and bureaucracies? Finally, we investigate how and why existing national systems of interest representation have come under pressure because of globalization: What are the consequences for the relation between labor and capital and how do different types of interest groups adapt to globalization?