This study examines Head Start's impact on children's cognitive and social-emotional outcomes by considering the quality of Head Start and heterogeneity in types of care received by the control group. The questions addressed in this article are (1) Do children who attended high-quality Head Start programs have better outcomes than those in low-quality Head Start, home-based, or center-based care and (2) Do child and family characteristics and overall quality affect child outcomes? This study found that high-quality Head Start children had higher cognitive scores than children in low quality Head Start or center-based care. Child and family characteristics and overall quality moderated the effects of type of care on children's cognitive and social-emotional outcomes. (author abstract)