It is increasingly clear that anxiety is a common and important co-occurring condition in ASD. The learning goals for this symposium range from the neurobiological underpinnings of anxiety and their relation to ASD, to comparisons of the clinical phenotype and treatment (behavioral and pharmacological) of anxiety disorders in children with and without ASD. This integration of basic and applied sciences, medical and psychological perspectives, will help to bridge gaps in our understanding of anxiety in ASD and facilitate novel directions for research.