Trauma is a widespread, harmful and costly public health problem. It occurs as a result of violence, abuse, neglect, loss, disaster, war and other emotionally harmful experiences. Trauma has no boundaries with regard to age, gender, socioeconomic status, race, ethnicity, geography or sexual orientation. It is an almost universal experience of people with mental and substance use disorders. The need to address trauma is increasingly viewed as an important component of effective behavioral health service delivery. Additionally, it has become evident that addressing trauma requires a multi-pronged, multi-agency public health approach inclusive of public education and awareness, prevention and early identification, and effective trauma-specific assessment and treatment. In order to maximize the impact of these efforts, they need to be provided in an organizational or community context that is trauma-informed, that is, based on the knowledge and understanding of trauma and its far-reaching implications.