Although the exact scope of commercial sexual exploitation of children (CSEC) remains unknown, its significant negative physical and emotional consequences for children has been well documented. However, there is little evaluation research to guide communities on prevention best practices and questions remain about what approaches can be effective. Not a Number (NAN) is a CSEC prevention education program developed by the non-profit organization Love 146. NAN is being delivered through a train-the-trainer model to groups of youth in Minnesota at-risk for CSEC. While it is a promising and evidence supported program, it has yet to be evaluated. The goal of this study is to evaluate the effectiveness of NAN in reducing rates of CSEC victimization for youth by using a rigorous cluster randomized controlled methodology in partnership with 24 youth-serving agencies in Minnesota. The research team will use a Community Based Participatory Research (CBPR) approach to implementing and understanding the evaluation. The 5-year study will be divided into two components. Component A (Study years 1-2) will involve: refining the study methodology; conducting a process evaluation of NAN implementation in Minnesota; qualitative data collection to understand community perspectives on prevention outcome goals, and pilot testing evaluation tools and methodology. Component B (Study years 3-5) will involve implementing the evaluation. Twenty-four youth serving agencies will be paired based on agency and community characteristics (e.g., agency size, community demographics, rural or urban location). Within each pair, agencies will be randomly assigned to an implementation condition (NAN administered within six months of the pre-test) or to a wait-list control condition (NAN program administered after 6-month follow-up surveys are completed by youth). Approximately 30 youth will be enrolled in the study per agency (N=720; n=360 per condition), with outcome data collected at 4 time-points: baseline, 6-week follow-up, 6-month follow-up and 12-month follow- up. The study, led by an experienced, multi-disciplinary team of researchers and practitioners, will represent the first rigorous evaluation of a CSEC prevention program. Findings will provide critical insight into the efficacy of education-based prevention for reducing CSEC victimization and inform future program development and prevention policy. This study addresses the CDC’s Research Priority 4 outlined in RFA-CE-22-003.