Participation in Early Intervention services can improve children’s cognitive, motor, behavioral, and language development, especially for infants born preterm or low birthweight, for whom the most rigorous research exists. Less causal evidence exists to support impacts on parent outcomes, but the research suggests mixed effects that lean in the beneficial direction. The current evidence base for Early Intervention focuses primarily on the developmental benefits that services can produce for infants and toddlers, rather than examining the impacts of a specific state-level policy. (author abstract)