The question of what policies may deter risk-taking actors who willingly commit suicide is not only theoretically challenging, but also of major importance to policymakers. Traditional deterrence theory, which is largely state-oriented, but has also delved into the realm of ordinary criminality, has not been adequately prepared to deal with individual or non-state actors who seem "irrational" because of their high propensity for risk taking and cost bearing. The present article seeks to adapt the notions of deterrence and risk taking developed in the context of interstate relations to such actors, especially terrorist groups whose members engage in martyr-style operations. First, a brief, non-technical review of the essentials of the rational choice approach to deterrence is provided. Second, the article indicates how this approach can be adapted to the deterrence of terrorist actions, especially the crucial role of risk and its correlate, uncertainty, on decision making. Finally, by way of examples, it suggests how these theoretical findings can contribute to a better understanding of the deterrence of terrorists' actions. Perhaps the most important conclusion reached is that no policy is best, although some policies appear to be more efficacious than others. Although this is not an unexpected conclusion, the present analysis puts it on a firmer theoretical foundation and reinforces the argument that the focus of debate, discussion, and policy should be on the prospects for containing or reducing terrorist actions via passive defenses and the denial to terrorists of access to potential targets.While bypassing the question of what might be "terribly wrong," the question of how to deter high cost and risk bearing terrorists, especially those who seek "martyrdom" in the conduct of attacks, is not only theoretically challenging, but also of major importance to policymakers. Although scholars agree that terrorists are rational in the senses that they pursue clear (in their own minds) goals and that their behaviors generally alter in expected ways in response to changes in the costs, risks, and probabilities, which are associated with different actions, traditional deterrence theory, which has been largely state-oriented (i.e., Realist and Cold War based) or focused on ordinary criminality, has been poorly equipped to deal with actors who appear to be irrational because of their high propensity for risk taking and extreme cost acceptance up to and including suicide. The present article seeks to explore the terrorist mindset through the examination of terrorists' goals, motivations, decision processes, risk taking, and the prospects for deterrence of them. The primary concerns revolve around the following questions: Psychologically, what does the emergent terrorist bring to a putative decision situation before any specific actions are contemplated? How might analysts and policymakers better understand, explain, and possibly predict actions and non-actions in these situations? In other words, how might terrorists be eff...