This paper explores issues and implications for diagnosis and treatment, stemming from the growing number of children identified with autism spectrum disorders (ASDs). Recent developments and innovations in special education and Medicaid programs are emphasized. Eligibility determination policies, innovations in diagnostic practices, the cost and financing of assessment, variability among programs in diagnostic criteria, and racial/ethnic disparities in the timing of diagnosis all influence the capacity of service systems to provide diagnoses in a timely, coordinated, accurate, economical, and equitable manner. There are several barriers to the more widespread provision of intensive intervention for children with ASDs, including lack of strong evidence of effectiveness in scaled-up public programs, uncertainty about the extent of obligations to provide services under the Individuals with Disabilities Education Act, high cost of intervention, and variability among states in their willingness to fund intensive intervention via Medicaid. Innovative policy experiments with respect to financing intensive intervention through schools and Medicaid are being conducted in a number of states.