New counterterrorism systems are spreading throughout the world. Many are based on behavior detection by skilled offi cers; others deploy techno-scientific theories and soft ware-mediated environments. All of these systems raise critical questions about scientific and legal evidence; profiling, costs, and effectiveness. However, much of the recent scholarship on this topic is based on secondhand information and fails to attend to key transformations in security discourses and in practice. Rather than offering just an overview and theoretical critique, this article draws from our ethnographic data on counterterrorism in the UK (with reference to the broader global securityscape) and examines the phantasmagoria of fears and threats, the experimentations, myriad “expert” theories, and productivity in this realm. In doing so, the article examines how, beyond utilitarian notions of efficiency and security, counterterrorism practices perform multiple cultural roles for those charged with its delivery. We discuss particular examples of counterterrorism deployments and explore the production of theories about the human in security discourses and practices.