In many parts of the world, people are dealing with the long-term effects of multigenerational trauma. Collective historical trauma affects intergenerational group experiences. This chapter explores theories of trauma, transgenerational trauma, and historical collective trauma. As an illustration, a clinical analysis is presented, based on positive transcultural psychotherapy, of the impact on the current mental and social well-being of residents of a small town in Poland, as evidence of a new wave of collective re-traumatization from past traumas of Communism, Stalinism, and World War II.