Data systems are tools to improve programs and, ultimately, outcomes for children and families. Young children with disabilities are served in early intervention and preschool special education programs, but they also may be served in other early childhood programs in their communities such as Early Head Start, Head Start, child care, and state prekindergarten. Having integrated early childhood data systems enables states to link data across these programs. These linkages provide powerful information about who programs are serving, what services they are receiving, and who is providing those services. Policymakers, state agency staff, local program staff, and others need high-quality integrated early childhood data systems to improve early intervention and preschool special education services and supports to better serve children and families and to answer important program and policy questions.