In this chapter we argue that the key to an understanding of international governmental organizations (IGOs) is to conceptualize them not as standard forms of organizations with individuals as their members, but as meta-organizations comprising organized actors as members. Meta-organizations are paradoxical constructions: autonomous actors with autonomous actors as members. Organizational elements cannot be considered in isolation in meta-organizations; their combination are key factors; therefore meta-organizations are often partially organized. IGOs are permanently competing for actorhood with their member states and this competition has far-reaching implications for to what extent they can make use of all organizational elements. Using one element may require the avoidance of other elements or certain forms of decision-making. This helps to explain why IGOs have problems achieving co-ordinated organizational action and why they are less powerful actors than standard organizations are. Yet IGOs are strong in other respects. The most important organizational element in IGOs is membership. The strengths of IGOs can be understood in relation to their creation, their expansion, and their long-term influence on their members.