This study examined the prevalence of ADHD symptoms and anxiety as reported by parents and teachers for 180 preschool children (ages 4-5) and school-aged children (ages 6-7) with ASD using the Child Behavior Checklist--Parent and Teacher Report Forms (Achenbach and Rescorla, Manual for ASEBA school-age forms & profiles, Research Center for Children, Youth, and Families, University of Vermont, Burlington, VT, 2001). Parents reported elevated anxiety symptoms in 31% of preschool children and 50% of school-aged children, while teachers reported lower rates of 5 and 30%, respectively. Parents reported elevated ADHD symptoms in 22% of preschool children and 45% of school-aged children, while teachers reported elevations in 20 and 24%, respectively. There was low concordance between parents and teachers, with teachers reporting fewer problems overall. Specific behaviors endorsed by parents and teachers are also discussed. [This is the online version of an article published in "Journal of Autism and Developmental Disorders."]