This article argues that the study of European integration is divided into two distinct approaches: classical integration theory for which the shape of the Euro-polity is the dependent variable; and the governance approach for which it is the independent variable. An historical and conceptual overview of the approach focuses on the efficiency side of governance and excludes issues of democracy and legitimacy. From a sociology of knowledge perspective, the first part traces the roots of the present discussion back to three bodies of literature, namely studies on Europeanization, regulatory policy-making and network concepts. The second part presents the achievements of the approach: putting EU studies in a comparative perspective, directing attention towards democratic governance and bypassing old dichotomies on the future of the nation-state. The final section evaluates present shortcomings, most notably a bias toward problem-solving, the proliferation of case studies and the lack of a coherent theoretical perspective.