In many clinical contexts, substance use disorder is oftentreated separately from posttraumatic stress disorder. Yet, these conditions commonly co-occur and are reciprocally determinant, meaning that the outcomes of a course of treatment for either condition might depend upon treating theother. On this episode, Dr. Sudie Back talks about the importance of treating co-occurring PTSD and substance use disorder simultaneously, and the prolonged exposure treatment, COPE, she developed with her colleagues to manage both disorders. Dr. Sudie Back is a professor, and the director of the NIH-sponsored DART research training program, in the Department of Psychiatry and Behavioral Sciences at the Medical University of South Carolina. She is also a psychologist at the Ralph H. Johnson VA Hospital.