Criminal justice system actors—from first responders to caseworkers and health care providers in correctional settings, to drug court judges and narcotics agents—are on the front lines of the opioid crisis in the United States. To inform their efforts, this report summarizes the nature, scope, and impact of opioid use disorder and its illegal distribution in the context of the criminal justice system and the epidemic’s impact on health, well-being, communities, and the criminal justice system.The report also describes criminal justice (and justice-related) responses to the crisis including the US Department of Justice’s Comprehensive Opioid Abuse Program and other efforts focused on the opioid crisis.