Children with Autism Spectrum Disorders (ASDs) are well-known for engagement in challenging behaviors. Unfortunately, due to its absence as a criterion for diagnosis in the "DSM-IV-TR", little attention has been paid to the endorsement rates of such behaviors. However, a recently developed measure to assist in the diagnosis of infants and toddlers with autism and PDD-NOS--the "Baby and Infant Screen for Children with aUtIsm Traits" ("BISCUIT")--has included a section designated for just this reason. This study used the "BISCUIT" to assess for significant differences in the endorsement rates of challenging behaviors between infants and toddlers with autism versus PDD-NOS as well as for significant differences between genders. There were significant differences between the diagnostic groups in endorsement rates of challenging behaviors as a whole, as well as among many specific behavior items. No significant differences between genders in endorsement rates of challenging behaviors were found. The implications of these findings are discussed. (Contains 2 tables.)