What do we know about young children with delays and disabilities, and how can we help them succeed in prekindergarten through third grade? To begin with, Kathleen Hebbeler and Donna Spiker write, identifying children with delays and disabilities to receive specialized services under the Individuals with Disabilities Education Act poses several challenges. First, even though eligibility is based on 14 disability categories listed in the law, each state determines its own criteria for those conditions. Second, young children--especially those with disabilities--are hard to assess. Third, deciding where to draw the line for eligibility along a continuum of functioning is a matter of policy rather than science. In recent decades, the authors note, the concept of disability has been moving away from a medical model that sees disability as an impairment that resides in the child and toward a framework that emphasizes children's functioning and interaction with their environments. The authors review effective ways to support development and learning among young children with disabilities, including language and social skills interventions, preschool curricula, instructional and other practices, and multi-tiered systems of support. Then they examine a critical policy issue: the inclusion of young children with disabilities in regular education classrooms. One critical finding is that high-quality instruction in general education classrooms is a major factor in good educational outcomes for children with disabilities, and for their successful inclusion from preschool to third grade. Moreover, improving the quality of general education benefits all children, not just those with disabilities. Hebbeler and Spiker also examine what we know about the transitions young children with disabilities make from one setting to another--for example, from prekindergarten to kindergarten. Here they conclude that we need far more research if we're to understand what makes such transitions successful.