Early Head Start provides services to low-income pregnant women and families with infants and toddlers with the goals of improving children’s development (cognitive, language, social-emotional, and health); fostering close supportive relationships between parents and their infants and toddlers; and encouraging the development of community partnerships. This report summarizes the interim results of an evaluation initiated in 1995 that includes about 3,000 children and families across 17 sites selected to represent a variety of environments (regional, rural, and urban), ethnic and racial compositions, and types of program approaches. At each site, children and families were randomly assigned to program and control groups; follow-up was carried out over three years of program participation, through a child’s third birthday. There was a consistent pattern of statistically significant (although modest) favorable impacts across a range of outcomes related to children and their families. The results found at the interim evaluation (conducted at age 2) were sustained through the child’s third birthday.