This is an Individual National Research Service Award for pre-doctoral research training, which provides predoctoral individuals with supervised research training in specified health and health-related areas leading toward the research degree (e.g., Ph.D.). Early identification of autism is critical to achieving the best possible outcomes for children. Delayed diagnosis translates into a missed opportunity to provide crucial services to reduce the disorder's severity and improve developmental outcomes and quality of life. Efforts to reduce age of diagnosis must be informed by a broader understanding of the mechanisms through which policies affect health practice and the extent to which health practice leads to improvements in child health outcomes. The proposed study will address these issues through the following questions: 1) To what extent do states' Early and Periodic Screening, Diagnosis and Treatment (EPSDT) policies affect child-level compliance with American Academy of Pediatrics (AAP) guidelines for well-child care?, 2) Are children with autistic disorder whose well-child care complies with AAP guidelines diagnosed earlier?, and 3) Is having a usual source of care independently associated with age of diagnosis, independent of adherence to these AAP guidelines? These questions will be investigated through an in-depth examination of service use claims over the two-year period prior to diagnosis in a sample of preschool- aged children who were enrolled in Medicaid sometime between 2001 and 2005. The proposed study has the potential to affect public health policy and intervention strategies in the areas of well-child care and the early detection and diagnosis of autistic disorder. In addition, findings may help to inform state policy decisions relative to the allocation of resources for the early detection of autistic disorder.