This chapter examines the organisational structure of the ecumenical synods. First, a new interpretation of their organisation is proposed. Whereas earlier scholars have argued for a (con)federal structure consisting of a leading group in Rome and quasi-independent local branches in the provinces, the sources indicate that the ecumenical synods were much more uniformly organised, with a central headquarters in Rome, local headquarters in certain cities and mobile delegations travelling along the agonistic circuits. Next comes an overview of synod officials and a discussion of the finances of the two associations. The chapter then proceeds to discuss the relationship between the synods and the emperor. Whereas several other scholars believe that the synods were a tool with which the emperor kept the agonistic world under control, it appears that the synods had more agency than was earlier assumed. Finally, this chapter analyses other agonistic associations in the Roman empire and their relationship with the ecumenical synods.