Friends and friendships are important structural parameters of human social life. Until recently, these two categories have been regarded as marginal, purely private phenomena and have thus been neglected in political science. Broadening this one-sided point of view, the author, Judith Gurr, systematically investigates friendship's role as a central political category.According to Aristotle's typology, political friendships are regarded as friendships of convenience based on the concept of philia. Serving as useful political and social capital by facilitating acquisition, accumulation and sustainment of power, they represent elemental instruments of power to political leaders and elites. Concerning modern political systems, this leads to the following important questions: What is the role of friendship in contemporary political systems? In what ways do political friendships affect the political processes and interactions in today's politics? The author elucidates these questions by investigating the interpersonal relationships of Margaret Thatcher and Tony Blair with their friends, clients and patrons.