This review has been commissioned by the Education Endowment Foundation (EEF) and Public Health England to identify priorities for improving practice in the support and management of children with delays in early language development between birth and five years (72 months). In addition, it has the specific objectives of highlighting interventions that have the greatest potential to improve children's life chances, reduce inequalities in outcomes, and potentially inform further rounds of research funded by the EEF. The review starts with an overview of the most recent findings associated with our understanding of early language and preliteracy development. It goes on to look at prevalence and at the proportion of children not attaining the appropriate levels of attainment in the early years. It then turns to interventions, their efficacy and effectiveness, and contextual factors that affect their implementation. Finally, the authors move on to the way that services are delivered on the ground in England and highlight the profile of five local authorities, the services they deliver, and factors affecting that delivery. The review ends with a summary of the main findings and recommendations for which interventions could usefully be taken forward. The appendixes provide summaries of the interventions identified and a table of interventions and their outcomes and then provide some additional details about the five case studies identified in Chapter 5.