The Early Head Start Research and Evaluation project, a rigorous, large-scale, random-assignment evaluation of Early Head Start, was designed to carry out the recommendation of the Advisory Committee on Services for Families with Infants and Toddlers for a strong research and evaluation component to support continuous improvement within the Early Head Start program and to meet the 1994 reauthorization requirement for a national evaluation of the new infant-toddler program. The Early Head Start Research and Evaluation project was funded in three waves. The Congressionally-mandated Birth to Three Phase (1996-2001) included an Implementation Study, an Impact Evaluation that investigated program impacts on children and families through their time in the program, and local research projects. In 2001, the Administration for Children and Families (ACF) funded the Pre-Kindergarten Follow-up Phase (2001-2004) to build upon the earlier research and follow the children and families who were in the original study from the time they left the Early Head Start program until they entered kindergarten. In 2005, ACF funded the Elementary School Follow-up Phase (2005-2010) to again build upon earlier research and follow the children and families from the original study while the children are in fifth grade, or attending their sixth year of formal schooling.