The National Head Start Impact Study has two primary goals. The first is to determine, on a national basis, how Head Start affects the school readiness of children participating in the program as compared to children not enrolled in Head Start. Does Head Start improve children's cognitive development, general knowledge, approaches to learning, social and emotional development, communication skills, fine and gross motor skills, and physical well-being? In addition, how does Head Start affect the lives of the families of children enrolled in the program? The National Head Start Impact Study is a longitudinal study that will involve approximately 5,000 - 6,000 three and four year old preschool children across an estimated 75 nationally representative grantee/delegate agencies in communities where there are more eligible children and families than can be served by the program. Data collection will continue through 2006, following children through the spring of their first grade year of school.