The environment is now an established area of theoretical and empirical work in the field of International Relations, but the central question remains whether existing institutional structures, intellectual and political, are being in some respect transformed by this development. This review article examines the concept of environmental security as a reflection of the centrality of the environmental challenge. This relatively novel perspective on a defining feature of the field tests the domain of discourse and inquiry, and thus has implications for the study of international relations, perhaps to the extent of justifying the enclosure of its key concepts within the environmental perspective.