The current study examined consistency between parental reports on early language development and behaviors in non-language domains and observer-coded videotapes of young children with and without autism spectrum disorder (ASD) and autistic regression. Data are reported on 56 children (84% male) with ASD (early onset or autistic regression) and 14 typically developing children (57% male) who had home videotapes. Unique to the current study is the independent identification of loss/no loss for each child by both parental report and observer-coded home videotapes and the examination of agreement between these two methods. Results indicate substantial concordance between parental report and observer codes for onset and loss of expressive language, but minimal concordance for loss in non-language domains, suggesting a need for supplementation of parental reports in these areas.