Part C early intervention is a federally funded program under the Individuals with Disabilities Education Act that serves infants and toddlers who have developmental delays. States are given the flexibility to define developmental delay under the program. Therefore, eligibility criteria for Part C services varies from state to state. This article compares estimates of the percentage of children who are likely to be eligible for early intervention in each state and Washington, DC, with the proportion of children who are served in each of those jurisdictions.

Using data from the Early Childhood Longitudinal Survey–Birth Cohort,  the proportion of children who would be eligible based on the numerical eligibility definitions currently in use across the United States were computed. The results showed that the proportion of infants and toddlers likely to be eligible for Part C services ranges from 2% to 78% across the United States. The proportion of children enrolled in Part C ranges from 1.48% to 6.96%.

This research documented substantial variability in the proportion of children who are likely to be eligible for Part C services.  Most states have adopted eligibility definitions that make many more children candidates for Part C early intervention than they serve. However,  current rates of enrollment are insufficient to serve all children with delays that fall under 2 SDs below the mean on any of the 5 developmental domains that are required to be evaluated by Part C regulations.