Intellectual and developmental disabilities include a heterogeneous collection of clinical characteristics, ranging from mildly compromised and largely autonomous to severely impaired and functionally dependent on others. Given the range of abilities and thus the range of needs, treatment availability and acquisition are often determined by the affected individual’s unique clinical presentation, severity of need, and access to social, financial, and community resources. Services for intellectual and developmental disabilities are available at the local, state, and federal levels and include direct service to the child or adult as well as support services for the larger family system. This entry describes the services provided and mechanisms for receiving these services from local providers, as well as through state and federal agencies and programs funded by these agencies.