Autism spectrum disorders (ASDs) impair multiple domains of health, mental health, and development throughout the life course. These pervasive impairments result in complex service needs that cut across sectors, change as people age, and demand a high degree of service coordination. Timely access to appropriate and well coordinated services has the potential to improve health, mental health, functional outcomes, and quality of life in adulthood, thereby reducing the public health burden of disease. Very little is known about how service use and insurance coverage change as youth with autism spectrum disorders age into adulthood or how these patterns of change are related to health and functional outcomes in young adulthood. Using data from a nationally representative and diverse cohort of 922 youth with ASDs followed over nine years into young adulthood through the U.S. Department of Education's National Longitudinal Transition Study 2, this research will characterize the changing service and health needs of youth with ASD as they become adults, discover resources and barriers associated with service utilization, and characterize young adult functional, behavioral, and health outcomes. This study will begin building a foundation of population-representative evidence that can inform the development and evaluation of services for the growing population of youth with autism spectrum disorders.