The study of international relations has been guided by two major paradigms, idealism and realism. The international system itself has undergone significant changes both is structure and process in the last two decades or so. The implications on the study of international relations as a result to these changes become the focal point of this paper. It explains the role of theory in international relations, the role of model and related methodological issues concerning concept, variable and hypothesis. It then proceeds to analyze the emergence of neorealism and neoliberalism. A better understanding of international relations calls for further research along these lines.