Behavioral IR faces a fundamental challenge. The actors in most IR models and theories are not individuals-they are aggregates like states, ministries, interest groups, political parties, and rebel factions. There are two broad approaches to attempting to integrate behavioral research about individuals. The first, a quasi-behavioral approach, makes nonstandard assumptions about the preferences, beliefs, or decision-making processes of aggregate actors. The second tries to build theories in which the key actors are individuals. Pursuing the former means that the assumptions about actors will be only weakly linked to the empirical findings propelling behavioral research. The second approach faces formidable obstacles that international relations theory has confronted for a long time and for the most part has not overcome.Behavioral economics has been one of the most active and productive areas of research in economics in recent years. Given the close methodological parallels between economics and rational-choice approaches to international relations (IR) theory, it is natural to ask how and to what extent the insights, ideas, findings, and, more broadly, the approach of behavioral economics will affect IR theory. The essays in this special issue try to provide a "framework for integrating the new behavioral revolution into international relations." 1 The issue "aims to chart a strategy for incorporating the new behavioral revolution more fully into international relations." 2 I offer some conjectures about the likely impact of the behavioral revolution on the study of international relations and highlight some of the challenges a truly behavioral approach to international relations theory faces. The ultimate impact, of course, will not be known for some time and will depend on the "research bets" scholars make and which of them pay off. 3 Watching those research bets play out in the coming years will be very exciting.The compelling empirical evidence driving behavioral economics is that individuals deviate in systematic ways from the predictions of the standard model. However, the actors in most IR models are not individuals-they are aggregates like states, ministries, interest groups, political parties, rebel groups, etc. Incorporating the empirical findings in IR models thus poses a significant challenge.There are two broad approaches to dealing with the mismatch between behavioral findings about individuals and the fact that the actors in most IR models and theories are aggregate actors. One approach, which might be called quasi-behavioral, is to 1. Hafner-Burton et al. 2017, S4. 2. Ibid., S3. 3. See Lake and Powell 1999 for a discussion of research bets in international relations.