ABSTRACT Goals of the parent project and proposed supplement: This is a request for an administrative supplement to the Guiding Good Choices for Health study (4UH3AT009838-02, MPIs Catalano, Kuklinski, and Sterling), which tests the implementation feasibility and effectiveness of embedding Guiding Good Choices (GGC), a group-based prevention program for parents of early adolescents, in three large, integrated healthcare systems serving socio- economically diverse families. GGC reduced adolescent alcohol, tobacco, and marijuana use, depression, and delinquent behavior in two prior randomized controlled trials. It also strengthened parenting practices and parent- adolescent relationship quality. GGC has the capacity to achieve population-level impact on adolescent health if made widely available through pediatric primary care. Having completed an intensive one-year planning phase that provided preliminary evidence of GGC?s fit within each of the three HCS, the investigative team is now embarking on a cluster-randomized trial of GGC in 72 pediatric primary care practices with approximately 3,600 families. Using a workflow that is easy to adopt, implement, and maintain, at each adolescent?s 12-year-old well visit, primary care pediatricians will recommend that parents enroll in the intervention. The team will use the RE- AIM framework to test implementation outcomes and effectiveness up to 3 years post-intervention, including hypothesized reductions in the study?s primary outcome of substance use initiation, secondary behavioral health problems (e.g., substance use frequency, mood symptoms), and exploratory outcomes (e.g., emergency department utilization). We will assess the feasibility and sustainability of GGC within each HCS, including health economic evaluation to assess costs in relation to value. Ongoing dialog with HCS stakeholders will help ensure implementation is aligned with HCS needs. Evidence of feasibility and effectiveness in three different HCS should foster broad dissemination to increase public health impact. Administrative supplement: This supplement award will fund GGC delivery in Spanish to monolingual Spanish-speaking and Spanish-preferring parents of 12-year- old Latinx adolescents. Latinos have historically experienced health disparities for many reasons, including limited access to linguistically and culturally relevant services. Latinx youth are particularly vulnerable to disparities with respect to prevalence, access to care, and treatment of behavioral health conditions like substance use and depression. These disparities highlight the need for effective and feasible preventive behavioral health interventions for this population delivered in trusted, non-stigmatizing settings. The supplement has three aims: 1) Conduct focus groups with monolingual and Spanish-preferring parents of adolescents ages 11-14, and interviews with pediatrician stakeholders, to ensure Spanish-language GGC is linguistically and culturally relevant and addresses modifiable barriers to uptake, 2) train Spanish-speaking interventionists to deliver Spanish-language GGC, and 3) deliver 2-3 Spanish-language GGC groups to approximately 36 parents and offer coach-supported self-administered GGC to up to 12 parents of 12-year old Latinx adolescents.