PROJECT SUMMARY/ABSTRACT Approximately 500,000 youth with autism spectrum disorder (ASD) will age into adulthood over the next decade. Transition to adulthood is a vulnerable time for youth on the autism spectrum due to fragmented systems of care coupled with ASD-related deficits in social communication and adaptive behavior. Youth who are disconnected from education or employment after high school graduation are at increased risk for poorer outcomes across the lifespan, such as poverty and mental health problems. Results from a recent systematic literature review revealed that low-income and racial/ethnic minority youth on the autism spectrum are twice as likely to be disconnected from education or employment after high school as their White and higher-income peers. As transition to adulthood is a critical period for setting up trajectories of adult functioning, this finding suggests that ASD disparities are likely to intensify over the transition to adulthood and perpetuate trajectories of poorer functioning across the lifespan for racial/ethnic minority or low-income youth on the autism spectrum. Conceptual frameworks for health disparities research suggest a three-phase model for addressing health disparities that includes detection of disparities, understanding why disparities exist, and development and evaluation of interventions to reduce disparities. While researchers have begun to document disparities over transition to adulthood in ASD, only one study to date has examined mechanisms linking sociodemographic factors to poorer transition-related outcomes. A next step toward a deeper understanding of mechanisms of disparities is often to employ mixed methods research. In mixed methods studies, qualitative research serves to contextualize quantitative findings and deepen our understanding of the processes underlying disparities. Accordingly, in this application, I propose a mixed methods study to investigate mechanisms of race/ethnicity- and income-based disparities over the transition to adulthood among youth on the autism spectrum. Mechanisms of disparities will be explored by (1) quantitatively examining mediators of disconnection from employment or education after high school, and (2) qualitatively characterizing barriers to effective transition to adulthood and ideas to ameliorate those barriers from the perspective of diverse adolescents and young adults on the autism spectrum and their families. The proposed research implements a community-based design in which a community advisory board of key stakeholders will actively shape all stages of the research. This collaboration will increase the relevance of findings and the feasibility of intervention recommendations. Ultimately, the results from this mixed methods study will inform the processes underlying sociodemographic disparities in disconnection among adolescents and young adults on the autism spectrum and inform future clinical applications. This proposal closely aligns with NIH ...