PROJECT SUMMARY Although there is evidence that autism spectrum disorder (ASD) can be accurately identified during the second year of life, and that early intervention can improve developmental outcomes, many children in the United States are not diagnosed with ASD until much later. Families seeking ASD evaluation often face barriers such as low availability of specialists, lengthy waitlists, and long distances to tertiary care diagnostic centers. This is especially true for children from traditionally underserved groups and communities. Without an innovative approach for prompt identification of ASD in young children, families and clinicians will continue to struggle with accessing and providing care. Telemedicine offers tremendous potential for addressing this need. However, there are few psychometrically sound, validated tools that can be administered remotely, via telehealth platforms, in order to guide service and action. We recently developed and evaluated a novel parent-administered/clinician- guided tele-assessment tool, the TAP (previously the TELE-ASD-PEDS; R21 MH118539). Initial successful studies within a controlled laboratory context yielded very high levels of family satisfaction with the experience, perceived utility by clinicians, and agreement regarding ASD risk classification with blinded comprehensive evaluation. Although promising, this work was limited by its reliance on controlled laboratory settings, a relatively small homogeneous sample, and use within a single research group. We have not yet validated the TAP for in- home use in a broader community sample, with novel groups of diagnostic clinicians, nor have we adequately demonstrated its value and impact for families representing traditionally underserved populations and areas. The current proposal represents the first rigorous evaluation of a tele-assessment tool for ASD with a large, diverse sample of children within their homes. In the current study, across two sites, we will recruit 360 toddlers (18-42 months) to participate in a home-based telemedicine evaluation using an ASD assessment tool explicitly developed for this purpose (i.e., the TAP). The sample will include children from the community who have screened positive on an ASD screener, as well as those referred from primary care and state early intervention systems. We will randomize families to receive assessment based on telemedicine alone or telemedicine plus an in-person evaluation, and then follow families over a 6-month time interval. This methodology will allow us to conduct rigorous psychometric evaluation of the TAP and comparison to widely used diagnostic tests, longitudinally evaluate service access and family engagement, and examine factors that affect diagnostic decision-making and family outcomes. This work has potential to transform the ASD evaluation process and dramatically improve access for traditionally underserved groups.