When establishing eligibility for developmental disability (DD) services, definitions of specific diagnostic conditions, such as autism, impact policy. Under the Medicaid home and community-based waiver program, states have discretion in determining specific program or service eligibility criteria, the nature of supports to be provided, and the number of individuals to be served. Individuals with DD, their families, and advocates have pushed to expand eligibility and improve the quality of services and supports received. This article uses a California legal case to explore the impact on individuals seeking eligibility for DD services when states rely on evolving diagnostic criteria for autism spectrum disorder. Recommendations are made for a more equitable and consistent approach to disability eligibility determination.