The paper identifies a class of violent acts that can best be described as sanctioned massacres. The special features of sanctioned massacres are that they occur in the context of a genocidal policy, and that they are directed at groups that have not themselves threatened or engaged in hostile actions against the perpetrators of the violence. The psychological environment in which such massacres occur lacks the conditions normally perceived as providing some degree of moral justification for violence. In searching for a psychological explanation of mass violence under these conditions, it is instructive to focus on factors reducing the strength of restraining forces against violence. Three interrelated processes are discussed in detail: (a) processes of authorization, which define the situation as one in which standard moral principles do not apply and the individual is absolved of responsibility to make personal moral choices; (b) processes of routinization, which so organize the action that there is no opportunity for raising moral questions and making moral decisions; and (c) processes of dehumanization which deprive both the victim and victimizer of identity and community. The paper concludes with suggestions for corrective efforts that might help to prevent sanctioned massacres by counteracting the systemic and attitudinal supports for the processes described.