The Medicaid program, a federal-state partnership administered by each state with oversight and funding contributions by the federal government, covers more people—including almost 40% of all children—than any other health insurance program in the United States. It is the primary means of coverage for specialized services needed by children with autism spectrum disorder, a range of developmental impairments including autism. This coverage is accomplished through legislation that permits the federal government to waive various statutory limits on state flexibility in benefit design. Research focusing primarily on children has found that Medicaid programs play an important role in supporting individuals on the autism spectrum in gaining and maintaining needed services and supporting their families and caregivers. However, there are important differences in the way states structure and implement their Medicaid programs that have not yet been fully cataloged. Moreover, research on enrollment and service use within the Medicaid program as these children age into adulthood is limited. Studies in this area are needed to ensure adequacy and equity in service availability and to guide states on policy and practice to meet the needs of these patients.