As part of The American Recovery and Reinvestment Act of 2009, the federal Head Start and Early Head Start programs received a significant increase in funding. Head Start is the longest-running program to address systemic poverty in the United States. It is also one of the most heavily researched programs in the nation. Still, debate continues about the program's effectiveness. Recent research, however, makes a case for investing in Head Start as a means of helping low-income children achieve better outcomes. Studies suggest that while gains may be small or moderate in some cases, participating in Head Start and Early Head Start gives children important advantages in cognitive development, health, and other domains. In addition, a recent study suggests that even impacts considered small can generate lifetime benefits that exceed the current $9,000-per-student estimated cost of Head Start. This Special Report is a summary based on the following publications: (1) "The Benefits and Costs of Head Start." "Social Policy Report" (Ludwig and Phillips 2007); (2) "Making a Difference in the Lives of Infants and Toddlers and Their Families: The Impacts of Early Head Start, Executive Summary." Washington, DC: U.S. Department of Health and Human Services, Administration for Children and Families (Love et al. 2002); and (3) "Supporting Families, Nurturing Young Children: Early Head Start Programs in 2006." "CLASP Policy Brief" ("Head Start Series") (Hoffman and Ewen 2007). This report discusses the results of studies evaluating the cost effectiveness and impact of the Head Start and Early Head Start programs. [This report was featured as the Special Report in the April 2009 issue of the Office of Child Development's newsletter "Developments."]