This study sought to understand the profile of and the factors which impact upon challenging behaviors among children with autism spectrum disorders (ASD) and multiple disabilities (MD). Teachers of 322 and 132 children with ASD and MD, respectively, attending special schools in Singapore, completed the Developmental Behavior Checklist, Teacher Version (DBC-T; Einfeld & Tonge, 1995). The findings suggest that children with ASD exhibit elevated levels of challenging behavior in all areas, relative to children with MD. Multiple regression analyses also indicate that diagnostic category was associated with all aspects of challenging behavior measured by the DBC-T. In addition, age was associated with only disruptive/antisocial behaviors in this study. Theoretical and practical implications were discussed. (Contains 2 tables.)