Early Head Start is a two-generation program for low-income pregnant women, and families with infants or toddlers that is designed to enhance children’s development and health and to strengthen family and community partnerships. A rigorous evaluation, the Early Head Start Research and Evaluation Project, was initiated the same time the program was authorized, following 3,001 children and families in 17 of the first programs funded. The children were randomly assigned either to the program group, or to the control group who were precluded from enrolling in Early Head Start, although they could receive other services in the community. The initial phase of the evaluation included an implementation study to document program services as well as an impact study, which followed children and their families until they were 3 years old with an ambitious measurement plan to assess the wide range of child and family outcomes that Early Head Start programs may influence. Two follow-up assessments have been conducted. Families were contacted in the prekindergarten year (when children were about 5 years old), and this latest wave of follow-up occurred when children were in fifth grade, about 10 years of age.