Under Part C of the Individuals with Disabilities Education Act (IDEA), participating states and jurisdictions must provide services to children who are either experiencing developmental delays, or who have a diagnosed condition that carries with it a high risk of developmental delay. Eligibility criteria used by the states influence the numbers and types of children receiving services, the types of services provided, and the cost of the early intervention system. This paper discusses how 50 states and 6 jurisdictions define developmental delay and summarizes their approaches to serving eligible children. It discusses the wide variability in the types of criteria states use to describe developmental delay and it identifies three categories of risk for adverse developmental outcomes used by many states. These include conditions of established risk, biological/medical risk, and environmental risk. Factors that may mediate the impact of risk factors are also noted, including temperament of the child, high self-esteem, good emotional relationship with at least one parent, and successful learning experiences. The summary table lists the following for each state: level of developmental delay required for eligibility; whether at-risk infants and toddlers are served; and comments. (SG)