Transatlantic international relations (IR) theory has more or less neglected the international relations of East Asia. This relative neglect has come in different forms: excluding East Asian cases from analysis, including East Asian cases but miscoding or misunderstanding them, or including them but missing the fact that they do not confirm the main findings of the study. A review of the East Asia–related literature on three important clusters of theorizing—structural theories of conflict, institutional design and efficacy, and historical memory—suggests that this neglect of the region (and other regions) may come at a cost to transatlantic IR, not only in terms of data problems but also in terms of omitted or downplayed explanatory variables and theoretical arguments.