PROJECT SUMMARY/ABSTRACT Obesity is a major health challenge of the 21st century, putting nearly one-third of adults and one-fifth of children and adolescents in the United States at risk for a range of health problems, including type 2 diabetes and cardiovascular diseases. Childhood obesity is now associated with a higher likelihood of obesity in adulthood, suggesting a vital role for early interventions. Research has identified a number of early life factors that affect childhood obesity; however, little is known about whether early childhood programs (i.e., preschool) affects childhood obesity. To address this critical evidence gap, this project builds upon an existing early childhood study — in which nearly 1,500 3-4 year-old children were randomly assigned to early childhood programs or to a control group — and measures the causal impact of preschool and parent programs on children’s diet, activity and obesity. Returning to the children who are now 6-10 years of age, we will compare early childhood program groups and control groups using data we will collect on diet, activity and obesity for up to 4 years. Our project will evaluate three new mediators underlying the effects of the programs, specifically children’s cognitive skills, their executive functions and related skills and parental involvement. Our study also examines whether there are differential effects by race, comparing the impact of the programs on Hispanic, African-American and Caucasian children. Understanding the causal impact of early childhood education on obesity is crucial for the development of public policies aimed at improving the health of the nation, particularly the widely debated policy on the public provision of preschool. Given the rise in childhood obesity and the disparities in health outcomes in the U.S., it is imperative to learn about whether such early childhood programs also have an impact on obesity.