Amid widespread policy interest in the numbers of individuals likely to be displaced by humanitarian crises, there is a growing weight of evidence that particular drivers, such as environmental change, may actually prevent rather than encourage movement 1 (Black et al. 2011; Gray and Mueller 2012b). There are obvious humanitarian reasons to be concerned about situations in which individuals are unable to move to escape danger, as such immobility both magnifies their vulnerability and may inhibit the access of humanitarian actors. Yet a research agenda investigating why populations might become “trapped” is still very much in its infancy, and faces a number of challenges. This chapter considers these challenges using the limited information on trapped populations in a variety of contexts globally. It sets out a justification for a research agenda on how and why people become trapped in times of crisis, and considers how research could progress in this currently very limited but potentially highly significant field. The chapter concludes with a consideration of the policy implications of this agenda.