PROJECT SUMMARY/ABSTRACT Autism spectrum disorder (ASD) is a common neurodevelopmental disorder affecting 1 in 54 U.S. children. Co-occurring anxiety affects 40 to 50% of children with ASD, causing substantial distress and impairment. Treatment of anxiety is a high priority for parents of children with ASD, and cognitive-behavioral therapy (CBT) modified for ASD has demonstrated efficacy relative to standard care CBT and usual care. However, existing protocols have been established for academic medical settings with limited stakeholder input and correspondingly diminished potential for real-world uptake in community-based clinics. Accordingly, we propose a study in which stakeholders from both rural and urban communities are fully engaged to develop a CBT intervention and associated clinician training protocol - Community-based Anxiety Program Tailored for Autism (CAPTA) - that is able to be readily employed in community mental health settings. We will then preliminarily evaluate treatment response and mechanisms. In Aim 1, we will conduct a needs assessment with parents of youth with ASD and co-occurring anxiety, community mental health clinicians, and community mental health clinic leaders; we will also consult with an Advisory Board of experts in CBT for co-occurring anxiety in youth with ASD and individuals with lived experience (i.e., parents and self-advocates). This feedback from stakeholders and experts will directly inform adaptations to CAPTA. We will then conduct a small open trial (N=10) with the goal of obtaining real-world experience and refining the treatment and measurement protocols. Aim 2 involves a pilot randomized controlled trial in which CAPTA is compared to usual care in two different community-based mental health centers (N=60). We will examine CAPTA’s preliminary effectiveness to improve anxiety symptom severity and impairment, and we will also explore theoretically oriented treatment mechanisms. Aim 3 focuses on implementation outcomes (fidelity, feasibility, acceptability) and contextual factors influencing CAPTA implementation and sustainment. The proposed project is well-aligned with recommendations from the Interagency Autism Coordinating Committee to scale up and implement evidence-based interventions in community settings, expand the services workforce, and accelerate the pipeline from research to practice. Specifically, this pilot study will establish the feasibility and acceptability of transporting CBT for youth with ASD and co-occurring anxiety to community mental health clinics before progressing to a larger hybrid effectiveness- implementation trial in an R01.