Trauma is one of the most important topics discussed throughout the clinical, social and cultural field. Social traumatization, as we meet it in the aftermath of genocide, war and persecution, is targeted at whole groups and thus affects the individual's immediate holding environment, cutting it off from an important resilience factor; further on, social trauma is implemented in a societal context, thus involving the surrounding society in the traumatic process. Both conditions entail major consequences for the impact and prognosis of the resulting individual posttraumatic disorders as well as for the social and cultural consequences. The volume connects clinical and epidemiological studies on the sequelae of social trauma to reflections from social psychology and the humanities. Post-war and post-dictatorial societies are in particular marked by the effects of massive, large group traumatization, and if these are not acknowledged, explored, and mourned, the unprocessed cumulative trauma that has become deeply embedded in the collective memory leads to periodical reactivations. To address social trauma, an interdisciplinary approach is required.