The International Monetary Fund (IMF) has been deeply involved in economic governance in developing countries through its conditional lending since the late 1970s. Despite the importance of the IMF in the economic and political life of its borrowers, we have, at best, an incomplete understanding of the roots of the institution's behavior. This dissertation attempts to answer some important questions about the IMF's lending activities, namely: why is there so much variation in the IMF's treatment of its borrowers? I argue that the IMF is best viewed as a purposive actor driven by a set of economic ideas. These ideas shape the way the institution's staff and management make decisions about the use of its resource in complex and unsettled political and economic circumstances. The IMF has political preference for policy teams composed of likeminded officials. I use new data to test the argument on three aspects of IMF treatment; the cross-national evidence shows that governments with a higher proportion of neoliberal policymakers receive larger loans with fewer binding conditions and are more likely to receive waivers for missed policy targets. Further, I show that the ability of top neoliberal economic officials to deliver better treatment from the IMF enables them to extend their time in office. Since the presence of the IMF confers political advantages to the policymakers that share the Fund's economic worldview, I argue that neoliberals have greater political influence in countries that have spent many years under the institution's conditional lending programs. The claims are tested using both quantitative analyses and a qualitative case study of Argentina's relationship with the IMF over a quarter century (1976-2001).