Early intensive interventions have been shown to be highly effective but are typically reserved for children carrying a formal autism spectrum diagnosis. Thus, accurate identification, as early as possible, is imperative. A measure that can identify ASD risk at a younger age offers the opportunity for intervention before the full symptom set of autism has emerged. This study aims to develop a new, video-based method of assessing early development. Taking advantage of thousands of hours of already collected and coded video of infants at risk for ASD, this research aims to create a video-based screening tool that depicts a range of social and communication behaviors. Collaborating with a company that develops software for families of children with autism, the researchers will create a secure website that parents can visit to view video, rate similarity to their infant’s behaviors, and ultimately identify video that best represents their child. This measure will be of low burden to families, as it is brief and can be administered in a confidential manner via internet. The first year of funding will be used to develop this new measure, called the Video-Referenced Infant Rating System for Autism (VIRSA), which will extend from 6 to 18 months of age. After an initial development and validation process, the VIRSA will be administered three times (at 6, 12, and 18 months of age) to parents of 50 infants, all of whom are at familial risk for ASD. This study will examine how reliable the measure is over time by examining the similarity between scores that a parent rates twice within a week. This phase will compare VIRSA validity of social and communication skill measures with scores on other established (but not video-based) social-communication instruments. Finally, the researchers will examine how feasible and useful parents perceive the VIRSA to be, comparing it to existing measures in ease of administration, time to complete, knowledge or expertise required, burden of the format, parent interest in the measure, relevance to the child, and perceived helpfulness in assessing development. In the future, this video-based instrument could have multiple research and clinical applications; for example, it could be used to monitor intervention progress, track development in pediatric settings to identify children requiring evaluation, and screen large community-based samples in public health settings.