Head Start provides comprehensive early child development services to low-income children, their families, and communities. In 1998, Congress determined, as part of Head Start’s reauthorization, that the Department of Health and Human Services (DHHS) should conduct a national study to determine the impact of Head Start on the children it serves. In October 2000, DHHS awarded a contract to Westat in collaboration with the Urban Institute, American Institutes for Research, and Decision Information Resources to conduct this study through spring of the children’s first grade year.