The article combines the argument about the social construction of reality with a power/knowledge approach to social reality. In this context it is argued that epistemic communities, by being an integral part of the knowledge/power equation, and by having an authoritative claim on knowledge, exercise decisive power in the ‘‘interaction game’’ of the construction of (world) politics. In the first two sections of the article the concepts of reality and epistemic communities are defined. In the third section a two-level model of epistemic communities’ action is developed, aiming at illustrating their role in the construction of world politics. The last section addresses the issue of the relationship between the epistemic and the political.