The end of the Cold War helped to prompt new interest in the study of ideas in international politics. Once the province of a few dedicated researchers on the fringes of the discipline, scholarship on the role of ideas now occupies an important place in the mainstream of North American and especially European international relations research. The five articles in this special issue of the journal are intended to move the research agenda on ideas and the end of the Cold War to a new level of rigor. They develop new models of how ideas affected the outcome and, in so doing, take stock of this event to refine our understanding of how ideas work in international politics. Although we seek a deeper understanding of the end of the Cold War itself, we also use this seminal case to clarify and advance the debate over the role of ideas in international politics more generally.