Therefrom the example of pharmaceutical industry, this chapter is an attempt to objectively assess the controversies and denunciatory discourses often focusing on collusion and conflict of interest. The alleged complicity between lobbies and public authorities is addressed in strictly sociological terms to evidence its systemic character. The hypothesis examined here is that the very logic of career development in the sector and its specialisation—in this case in the field of medicines—is conducive to the crossing of institutional borders between the public and private arenas. The first part examines the career logic of these lobbyists who defend the interests of the pharmaceutical industry in Brussels by contextualising them within a broader space of representation. It evidences a circulation from federation to firms. The job market that is offered to lobbyists extends far beyond the industry, which points to the porosity of borders between public sphere and private interests. The second part explores the idea of the making of a group as a result of these career and circulation logics.