To determine any variation that might occur due to the type of assessment and source used to assess them, the prevalence of 7 anxiety disorders were investigated in a sample of 140 boys with an Autism spectrum disorder (ASD) and 50 non-ASD (NASD) boys via the Child and Adolescent Symptom Inventory and the KIDSCID Clinical Interview. Boys with an ASD were significantly more anxious than their NASD peers. Data collected from the boys with an ASD themselves showed differences in the severity and diagnostic criterion of anxiety disorders to data collected from the boys' parents. There were age-related variations to the pattern of anxiety disorder differences across reports from the boys with an ASD and reports from their parents.