The Early Head Start Research and Evaluation Project included studies of the implementation and impacts of Early Head Start. The research was conducted in 17 sites representing diverse program models, racial/ethnic makeup, auspice, and region. In 1996, 3,001 children and families in these sites were randomly assigned to receive Early Head Start services or to be in a control group who could utilize any community services except Early Head Start. Children, families, and children’s child care arrangements were assessed when children were 14, 24, and 36 months old, and families were interviewed about services at 7, 16, and 28 months after random assignment. Child assessments included a wide array of child cognitive, language, and social-emotional measures using direct assessment and parent report. Parent assessments included observation (videotaped and by interviewers) and self-report. Families in the program and control groups were demographically comparable at baseline and assessment points. Several research briefs have been published based on findings from this study. A prekindergarten followup was completed and a 5th grade followup is currently underway.