This collection underscores the point that Southeast Asia is now an important site for applying new theories of international relations. It also demonstrates that theoretical frameworks originally developed in North America and Europe have to be adapted to the specific circumstances found in places like Southeast Asia. The recent proliferation of theories of international relations has transformed analyses of Southeast Asia’s international affairs. A new generation of scholars has promoted a lively and illuminating debate which has seen the traditional realist/ neorealist approach, which continues to hold centre stage, challenged by constructivist analyses. In turn, constructivists have found themselves under fire from an array of competing approaches. This collection engages this emerging debate. It underscores the point that Southeast Asia is now an important site for applying new theories of international relations. It also demonstrates that theoretical frameworks originally developed in North America and Europe have to be adapted to the specific circumstances found in places like Southeast Asia and that this process can enrich theory building. The chapters in this book focus on the realist/neorealist, constructivist, English School and critical approaches. The resulting debate helps to shed light on ways of analysing Southeast Asian relations as well as on the evolution of these key theoretical frameworks. This book was published as a special issue of The Pacific Review.