A historical and psychological study of genocide is presented in which special emphasis is given to modern manifestations of this phenomenon. The policy of eradication of the Jews by the Hitler regime is considered as an example of genocide in the twentieth century. The psychopathology of genocide and the complex relationships among aggressors, victims and witnesses are elaborated. Inferences are drawn from past and present patterns of genocide that may provide some leads to the future. It is now possible to envisage an all-consuming genocide unless nations can learn to live together, not necessarily in unity but in diversity.