Autism spectrum disorders affect as many as 1 out of 150 children (Centers for Disease Control, 2007), with many higher-functioning children not being diagnosed until elementary school or later (Fombonne, 2003). Significant impairment in social, adaptive, and school functioning is prevalent and longstanding (Howlin et al., 2004). In addition, comorbid psychological disorders are common in the ASD population (Simonoff et al., 2008), and may cause substantial distress and impairment beyond that caused by the ASD diagnosis. Comorbid anxiety disorders, in particular, affect as many as 80% of children and adolescents with ASD (Bellini, 2004; de Bruin et al., 2007; Klin et al., 2005; Muris et al., 1998). Although efficacious interventions have been developed for otherwise typically developing youth with anxiety disorders, the linguistic; cognitive; and social characteristics of ASD may render standard treatment approaches less effective for children with ASD (Volkmar & Klin, 2000). Thus, there is a clinical need for the modification of existing treatment modalities for this unique group. To date, few studies have experimentally tested the efficacy of CBT for youth with a comorbid presentation of anxiety and ASD. This gap in the literature is of particular concern given the prevalence of comorbid anxiety among children, consequences of untreated anxiety, unknown efficacy of antidepressant medication for anxiety in ASD, and potential safety and tolerability issues related to medication use. Accordingly, we are proposing a randomized controlled trial to examine the efficacy of CBT relative to treatment as usual (TAU) in 46 youth ages 7-11 with ASD and comorbid anxiety disorder(s). In the proposed grant, we will: (1) examine the acute efficacy of CBT relative to TAU, and (2) evaluate the short-term maintenance of treatment gains. Forty-six children (ages 7-11 years) with ASD and comorbid anxiety disorder(s) will be randomly assigned to one of the two treatment conditions. Primary outcomes will be assessed by an independent evaluator, and will include change in anxiety symptom severity; response rates; and remission rates. Considering the rising number of children diagnosed with ASD, our proposed work toward the advent of an efficacious CBT protocol will provide a timely contribution to public health efforts.