ABSTRACT Increasing underrepresented minority (URM) participation in the biomedical workforce is essential to ensuring scientific diversity and meeting the growing demand for STEM graduates. Inadequate URM representation in STEM has historically been fueled by lack of access to professional resources and educational opportunities, leading to low rates of retention of URMs in STEM degree fields. Theoretically-grounded, mentored research experiences have been shown to address these barriers and increase URM persistence in STEM fields. However, few structured, comprehensively evaluated programs exist and most focus on undergraduate and post-baccalaureate students, as opposed to the critical foundational period of high school. Thus, the primary objective of the proposed mentored research program, titled MUSC High School Teen Science Ambassador Program, is to provide early clinical research experiences and professional development to high school students with the long-term goal of increasing diversity and helping meet the growing need in the biomedical workforce. The program will be supported by MUSC?s Youth Collaborative, which is comprised of faculty and trainees focused on adolescent substance use and mental health research, which will provide a rich training ground for real-world research experiences. The proposed program is aligned with NIH?s mission to support educational activities that complement and enhance the training of a workforce to meet the nation?s biomedical, behavioral, and clinical research needs as outlined in PAR-20-153. The specific aims of the Teen Science Ambassador Program are to: provide courses for skills development and hands-on research experiences, as well as mentoring and professional development training to youth interested in STEM careers. This will be accomplished through three focused phases: (1) a 16-week, mentored didactic training on clinical research skills and professional development, including completion of a literature review, oral presentation, and public service announcement; (2) near-peer mentorship training and experience, as well as an internship in an NIH- funded lab focused on adolescent substance use research; and (3) continued networking with peers, faculty, and alumni for long-term career success. Input from community stakeholders and an Advisory Committee will be collected to assess and improve program goals and outcomes, and all program materials will be made publicly available for dissemination and implementation at other institutions. The highly-qualified, multidisciplinary faculty mentorship team, partnerships with community schools and leaders, and rigorous program evaluation from independent evaluators will ensure that the proposed program meets the stated objective to increase diversity in the biomedical workforce.