PROJECT SUMMARY Children with autism and anxiety exhibit significantly more self-injurious behavior, more depressive symptoms, poorer relationships with teachers, peers, and family members, and higher levels of aggressive behavior relative to children with autism without anxiety symptoms. Yet, identifying anxiety in autism populations can be difficult, emphasizing the need for objective measures of anxiety. Additionally, autism research has historically excluded Black/African American and other minorities. Therefore, investigating developmental risk and protective factors that are associated with anxiety symptoms within a more racially diverse autistic population is critical to prevent or reduce negative mental health outcomes. Therefore, the current study aims to collect a large sample of autistic and nonautistic adolescents to evaluate whether the presence of atypical autonomic activity is a biomarker of anxiety in autistic youth. This proposal has three aims: 1) to investigate the association between baseline autonomic activity and anxiety levels in adolescents with and without autism; 2) to examine the role of ecological context and race and their relation with baseline autonomic activity and anxiety in adolescents with and without autism; and 3) to utilize real world experience sampling and noninvasive heart rate monitors to capture real-time data on autonomic activity, anxiety levels, and ecological context in the natural settings of adolescents with and without autism. Such knowledge will allow for identification of anxiety in autistic youth that would otherwise be unable to report on anxiety and inform the development of interventions that are generalizable to a racially diverse population. In the proposed K08 career development plan, I will undertake training in the Maryland Center for Health Equity including field observations in the Black/African American community to explore aspects of the ecological context and how those experiences relate to autonomic activity and anxiety in a racially diverse sample. Additionally, I will acquire core knowledge in psychophysiology as related to the parasympathetic nervous system, develop expertise in the assessment of anxiety, receive advanced training in quantitative methodology for multilevel modeling of intensive longitudinal data, and training in ecological momentary assessment best practices. Successful completion of these aims would lay the groundwork for validating the use of autonomic activity as an objective transdiagnostic biomarker of anxiety in autism and contribute to the development of targeted interventions that promote emotional well-being, empower youth with autism from diverse backgrounds, and improve their overall quality of life. Completion of the training goals will prepare me as an independent researcher in the fields of autism, developmental psychopathology, and clinical science with experience in recruiting and working with diverse populations.