This thesis deals with the supranational organization of European trade unions. The European trade union movement is, via its umbrella organization the ETUC, an institutionalized social partner within the European Union. The ETUC is a very diverse organization with great potential of conflicting interest among its members. This thesis therefore seeks to explore the dynamics and interest heterogeneity of the ETUC. Drawing on previous research and literature it formulates a number of hypothesises to test what variables that influence the member organizations policy preferences (i.e.