This Mentored Clinical Scientist Development Award (K08) will provide the education and skills that I need to make two important transitions in my career: (1) from researching adult sexual minorities (i.e., gay, bisexual, lesbian, transgender) to researching adolescent sexual minorities, and (2) from researching risk factors for health problems to developing and evaluating the efficacy of prevention interventions. Relative to their heterosexual counterparts, sexual minority adolescents are at increased risk for substance use, suicidality, and in males, HIV-infection. Despite these facts, virtually no research exists on prevention with sexual minority adolescents. Although existing prevention interventions designed for heterosexual adolescents may be effective for sexual minorities, research suggests that sexual minority adolescents experience unique stressors (e.g., anti-gay harassment, victimization, or family rejection) that may facilitate the r risk behaviors. These issues are not addressed in standard prevention programming. Thus, intervention models that address the unique experiences of sexual minority adolescents are needed. My long-term career goal is to develop and test the efficacy of interventions that aim to prevent substance use, sexual risk behavior, and suicidality in this vulnerable population. This will require additional training and mentorship in several areas: (1) adolescent development, (2) models of adolescent risk behavior and prevention, (3) intervention development, and (4) evaluation research and advanced quantitative methods. In addition to the training plan, this proposal also outlines a research plan that will further support my transition into an independent, NIH-funded investigator. This research will comprise 3 phases: (1) assessing the current practices and capacities of community-based organizations that serve sexual minority adolescents, (2) gathering quantitative data designed to test how sexual-minority-specific stress (e.g., victimization and family rejection) contributes to these adolescents' sexual risk behaviors, substance use, and suicidality, and (3) using this knowledge to develop an intervention and pilot its feasibility and acceptability in a community setting. Data gathered in each of these phases will directly support a subsequent RO1 application in which I aim to test the efficacy of an intervention designed to prevent sexual risk behavior, substance use, and suicidality in sexual minority adolescents.