Home visitation has emerged as a key strategy for promoting child and family well-being in the current policy context. This article examines the effectiveness of the Early Head Start (EHS) home-based program for children and families at the end of the program and 2 years later, with a particular focus on the role of program implementation in the impacts of the EHS home-based program on child and family outcomes. There was a pattern of broad, modest effects of EHS home visiting for both children and parents, which were strengthened if the programs were fully implemented according to federal guidelines. In particular, impacts for children in the cognitive and language domain were documented. Implications of these findings for policy and practice are discussed. (Contains 5 tables.)