Decades of research have identified substantial benefits from participation in high-quality preschool programs for both individual children and their communities. This issue brief summarizes key findings from a study of disparities in access to preschool in Illinois. The purpose of the study is to aid efforts to realize these benefits for children and communities across Illinois by providing an overview and analysis of existing preschool opportunities and outstanding needs in our state. This issue brief begins with an overview of research evidence on preschool disparities from nationally representative studies, followed by an examination of the impact of funding cuts to Preschool for All in Illinois. We then present findings on participation in all public and private preschool programs in Illinois from the U.S. Census Bureau's American Community Survey (ACS), examining disparities related to family income and race-ethnicity, as well as geographic areas within the state. We conclude with a discussion of policy implications for Illinois. We emphasize the need to provide new funding for preschool, target resources to increase enrollment of underserved populations, invest in quality improvements, and strengthen community capacity to offer early learning opportunities. (author abstract)