The Biomarkers in autism of aripiprazole and risperidone treatment (BAART) project will provide evidence-based guidance in the selection and monitoring of drug treatment of autism. BAART involves 3 academic centers across South Carolina. Although the FDA has approved use of the antipsychotic drug risperidone for irritability associated with autistic disorder, a moderate response rate in pivotal clinical trials and concerns over tolerability and weight gain can force clinicians to select alternative drug treatments for which evidence-based support is sparse.