Part C of the Individuals with Disabilities Education Act (IDEA) was established to ensure that infants and toddlers with disabilities, from birth to age 3, and their families receive appropriate early intervention services. Within the Department of Education (Education), the Office of Special Education Programs (OSEP) is responsible for awarding and monitoring grants to states for Part C according to IDEA requirements. To address questions about how states have implemented IDEA Part C, this report provides information on: (1) how Part C programs differ in their eligibility criteria and whom they serve; (2) to what extent states differ in their provision of services and funding; and (3) how Education and state lead agencies help support and oversee efforts to implement Part C, such as identifying children for services and transitioning children to follow-on programs, such as IDEA Part B. GAO recommends that Education provide states with additional guidance on transition planning and services, especially for children who would enter Part B during the summer. In comments on our draft, Education cited an ongoing study of general transition issues. When Education verifies the results of its study, it should use that information to inform guidance to states on transition planning. [This report was produced by the United States Government Accountability Office.]