Despite their potentially central role in fostering school readiness, executive function (EF) skills have received little explicit attention in the design and evaluation of school readiness interventions for socioeconomically disadvantaged children. The present study examined a set of five EF measures in the context of a randomized-controlled trial of a research-based intervention integrated into Head Start programs (Head Start REDI). Three hundred fifty-six 4-year-old children (17% Hispanic, 25% African American; 54% girls) were followed over the course of the prekindergarten year. Initial EF predicted gains in cognitive and social-emotional skills and moderated the impact of the Head Start REDI intervention on some outcomes. The REDI intervention promoted gains on two EF measures, which partially mediated intervention effects on school readiness. We discuss the importance of further study of the neurobiological bases of school readiness, the implications for intervention design, and the value of incorporating markers of neurobiological processes into school readiness interventions.Growing up in poverty significantly increases the likelihood that children will start school well behind their advantaged peers in key areas of language development and emergent literacy skills (Zill et al., 2003). Perhaps even more critically, many will start school without the social-emotional maturity and classroom behaviors that foster "readiness to learn," impeding their rate of progress once in school, and contributing to gaping disparities in school performance, high school graduation rates, and long-term employment potential (Campbell & von Stauffenberg, 2008;McClelland, Acock, & Morrison, 2006;Ryan, Fauth, & Brooks-Gunn, 2006). Rates of child poverty are on the rise in the United States, now affecting nearly one out of five children (Children's Defense Fund, 2005), making the problem of understanding and promoting school readiness a national priority.Recent efforts to promote school readiness for children growing up in poverty have focused on improving the instructional content of preschool programs, particularly Head Start programs, to enhance children's acquisition of key emergent literacy skills (such as letter identification and phonemic sensitivity) that are strong predictors of later achievement (Lonigan, Burgess, & Anthony, 2000). Although important, instructional strategies that focus narrowly on promoting the memorization of discrete content may "miss the mark" developmentally. The long-term impact of preschool interventions may depend on the degree to which they foster the development of mental systems that support learning and adaptive learning behaviors (Blair, 2002). For this reason, the Committee on Integrating the Science of Early Childhood Development (Shonkoff & Phillips, 2000) and others have underscored the importance of promoting self-regulation and social competence in preschool Copyright ©2008 Cambridge University Press Address correspondence and reprint requests to: Karen Bierman, Pennsylvania ...