The Aberrant Behavior Checklist (ABC) is a widely used measure in autism spectrum disorder (ASD) treatment studies. We conducted confirmatory and exploratory factor analyses of the ABC in 1,893 children evaluated as part of the Autism Treatment Network. The root mean square error of approximation was .086 for the standard item assignment, and in exploratory factor analysis, the large majority of items continued to load on the originally assigned factors. Correlations between the ABC subscales and multiple external variables including the Child Behavior Checklist and demographic variables supported the convergent and divergent validity of the ABC as a measure of behavior problems in ASD. Finally, we examined the impact of participant characteristics on subscale scores and present normative data.