International governmental organizations (IGOs) constitute the institutional grid of global governance. In order to shed light on the conditions under which they influence policy making, scholars have put forward various concepts to capture meaningful empirical variation among groups or samples of IGOs. However bureaucratic features of IGOs have largely remained on the margins or even outside the scope of these efforts. Conscious of this gap this article puts the concept of “autonomy of international bureaucracies” at center stage. It develops a composite index in order to measure what is conceived of as structural or formal autonomy of secretariats of IGOs. The usefulness of the suggested index is subsequently discussed on the basis of data collected for 15 international organizations. The article ends by recommending greater dialogue between scholars studying international institutions and national administrations. Intensifying joint efforts seem promising for the simple reason that growing relevance, permanence and size of IOs raise precisely the kinds of organizational questions (about bureaucratization, responsiveness, control, legitimacy and the like) that lie at the heart of public administration as a discipline. In view to analyzing international bureaucracies there appears to be ample opportunity for mutual theoretical fertilization between students of international relations, regulatory agencies, organizational theory and public administration.