This investigation consisted of two studies designed to look at the underlying structure of the Autism Spectrum Disorders-Diagnostic for Children (ASD-DC). Study 1 was a factor analysis of the 40-item informant based scale with 149 children, 2-16 years old, who met criteria for an ASD. A four factor solution consisting of social relationships, nonverbal communication/socialization, verbal communication, and restricted interests/insistence on sameness was obtained. For study 2, these 149 children were compared to 125 peers who were either typically developing or had a non-ASD diagnosis on the four factor structure established in study 1. Children with ASD displayed significantly more symptoms on all four factors of the scale. Implications of these data are discussed.