What can the sociology of lobbying professionals tell us about the relationships between European institutions and interest groups and about the latter’s ability to influence EU policies? This chapter begins with an overview of the academic literature on EU lobbying, looking at its main focuses and the reasons why little attention has been paid to lobbyists themselves. It then presents the sociological perspective adopted in this book, its main hypotheses and methods and the specific questions it aims to explore. Finally, it refers to specific studies taking this approach, in particular, the subsequent chapters, to examine two key dimensions. The first (what do lobbyists do?) concerns relationships between EU institutions and interest groups and their transformation as the result of reforms undertaken in Brussels in terms of human resources, decision-making processes and transparency. How has the ‘normalisation’ of lobbying affected lobbyists’ practices and the role they play in shaping EU policy? The second dimension (who are these lobbyists?) concerns changes in lobbyists’ profiles and career paths. Does the standardisation of lobbying practices go hand in hand with a homogenisation of career paths, recruitment rationales and lobbying organisations’ capacity for action?