Psychosocial traumatic events, and interpersonal violence experiences in particular, during childhood serve as strong and consistent predictors of substance use problems (SUP) during adolescence and adulthood. PTSD that extends from such IPV often co-occurs with SUP. Despite this well-established link, standard care for adolescents with co-occurring SUP and PTSD for the last several decades has been to treat these problems separately. This compartmentalized approach to treatment creates burden on teens and families, raises unique challenges to clinicians in both mental health and addiction domains, and may contribute to high rates of SUP relapse among adolescents with co-occurring PTSD. To address this problem, our team recently completed a rigorous NIDA-funded randomized controlled trial (RCT) supporting the efficacy of an integrative, exposure- based treatment we developed, Risk Reduction through Family Therapy (RRFT), in greater long term reductions in SUP, as well as PTSD avoidance and hyperarousal symptoms, in comparison to standard treatment in a large teen sample. The proposed RCT, with an effectiveness-implementation Hybrid Type I design, substantially builds on that prior research by proposing to: 1) evaluate whether RRFT's clinical effectiveness for reducing SUP and PTSD can be extended to youth in outpatient substance use treatment settings—where youth are presenting for SUP treatment and where clinicians often have less experience treating PTSD (Aim 1); 2) evaluate the cost- effectiveness of RRFT and to explore inner context variables (e.g., perceived treatment acceptability, attitudes, and satisfaction among the participating adolescents, caregivers, agency leaders, and therapists and barriers to and facilitators of implementation) that might affect RRFT implementation in diverse practice settings (Aim 2). The proposed effectiveness-implementation trial will recruit adolescents (13-18 years) with a history of IPV presenting with SUP and PTSD symptoms for outpatient substance use disorder treatment at sites in Denver, Colorado affiliated with NIDA's Clinical Trials Network. Participants will be urn randomized to RRFT or Treatment as Usual. A multi-method, multi-respondent approach will track clinical outcomes (SUP, PTSD, and putative targets of treatment, such as emotional suppression) at 3, 6, and 12 months post-baseline. To reduce the science-to-practice gap, as an Exploratory Aim, we will assemble and engage an Advisory Board of leaders from Colorado state departments (Offices of Behavioral Health and Criminal/Juvenile Justice for Colorado, which have committed to participate) and community mental health organizations that oversee policy and decision- making in selection and implementation of psychosocial treatments for high-risk adolescents, with the goal of building capacity for large scale (e.g., state-wide) uptake of evidence-interventions for teen SUP and PTSD, like RRFT, upon completion of the grant. This proposal is directly...