Few reading this Journal would argue with the assertion that both the substance and the study of world politics are now characterized by a seemingly endless process of change. The proliferation of political issues, especially those labelled “post-industrial“, and the recognition of transnational phenomena, among other factors, have greatly increased the number of problems considered ‘legitimate‘ by the scholar and practitioner. Yet we have long been made aware of many of these problems by the remarkably prescient ‘functional’ writings of one man, David Mitrany. Whenever ‘functionalism’ is used in the context of world politics or regional integration the obligatory reference is to Mitrany's A Working Peace System and, until very recently, he continued to provide the intellectual force behind the approach. The books considered in this review offer description, application and criticism of functionalism from different perspectives and with different empirical references, but the central thread remains Mitrany's conceptualization of the approach.