In this chapter we seek to highlight the importance of advancing the work that does exist on GPSFs in the institutionalization of transnational governance regimes through a more careful consideration of the identities, projects and effects of the firms in question. We contend that in their attempts to develop new markets, services and more efficient internal organizational models, GPSFs exercise far reaching institutional effects as they challenge governance regimes, disrupt/create jurisdictions, and transform identities, practices and systems of regulation in the professions themselves. They do this, we suggest, through three strategies associated with scope of control, defining scales of knowledge resources, and the production of ecologies of linked interests. These strategies involve developing strategic alliances with a range of other field actors such as academia, regulatory bodies, International Organisations, national governments and professional associations as part of linked ecologies (Abbott, 2005). As such, GPSFs exemplify the process of professional strategy > organizational opportunities > issue control that Seabrooke and Henriksen (this volume) claim is central to the transnational realm. This chapter provides, then, a contribution to on-going attempts to ‘revisit theories of professionalism, which did not fully anticipate the shift of professional work to the context of large organizations’ (Suddaby et al., 2007: 25). It also complements the following chapter by Boussebaa, outlining the institutionalizing effects of neo-colonial networks.