There is a need for valid, unbiased treatment response measures for ASD , as studies report improvements even in control conditions and results are confounded by the reliance on parent/clinician reports. To address this need, the Brief Observation of Social Communication Change (BOSCC) is being developed which is a coding scheme that is sensitive to subtle changes in ASD features. The BOSCC, currently applicable for minimally verbal toddlers, measures behaviors during videotaped play interactions with a parent or clinician. The BOSCC has shown promising preliminary results although further validation is needed. This project aims 1) to compare BOSCC results to clinicians’ impressions of improvement, 2) to determine the BOSCC’s utility when applied to segments of ADOS administrations, and 3) to expand the BOSCC to older, verbally fluent individuals. The BOSCC has the potential to provide an effective measure of change in ASD symptoms, enabling researchers to better identify efficacious interventions, tailor treatments, and, ultimately, improve the lives of persons with ASD.