The prevalence of challenging behaviors in the autism spectrum disorders (ASD) population is often assumed to be high but relatively little research has actually been published on it. Furthermore, challenging behaviors are likely to impede progress in evidence-based treatment programs, such as early intensive behavioral intervention (EIBI). Little or no previous research has evaluated the prevalence of various topographies of challenging behavior in a population of children with ASD receiving EIBI services, nor evaluated the relationship between such behaviors and the severity of ASD symptoms. Using data from the ASD-DC and the ASD-BPC in 84 children with autism receiving EIBI services, the current study conducted a regression analysis of relations between endorsement of challenging behaviors and ASD symptom severity. Results indicated that 94% of the sample reported the presence of challenging behavior, stereotypical behaviors were the most commonly reported, and that the presence of challenging behavior was predicted by ASD severity. (Contains 2 tables.)