Mass violence carries with it an enormous impact on health; the psychological impact is well recognized but poorly understood. There is a need for health professionals around the world to learn basic issues about the psychological impact of violence and to have available more specialized training to equip them with skills necessary to work directly with victims of mass violence. Organizing mental health services in conflict and in post-conflict situations requires many skills and complex work across sectors. Understanding mass violence from a public mental health perspective provides a framework for a curriculum that covers treatment for individuals and interventions for populations as well as exploring the mental states and social relationships which promote peace. Training implications are broad and should take account of individual and population needs, but also of a deeper human need to understand and contain that violent side of our nature that threatens us with extinction.