This chapter explores the association between terrorism, mental health and the capacity to provide evidence-based mass casualty intervention from a global perspective. The main message is there are vast differences in these three areas across countries and that, especially the last of the three, variation in service capacity and supportive conditions, influences the chances of implementing evidence-based guidelines. Consequently, it will be easier to provide evidence-based cost-intensive therapy and treatment to affected populations in less vulnerable countries with well-developed healthcare systems than in resource-poor environments. It is important to better understand alternative interventions and mechanisms and societal options for care delivery in more vulnerable countries, and to develop strategies to utilize them effectively. Systematic enquiries can strengthen the evidence base of guideline implementation across different local contexts of terror-focused aftercare. Importantly, the future development of new lower intensity interventions, guidance and the potential to anticipate vulnerabilities can particularly benefit low resource countries.