The Early Head Start Research and Evaluation (EHSRE) Study was conducted by Mathematica Policy Research (MPR) and included five major components: (1) an implementation study; (2) an impact evaluation, using an experimental design; (3) local research studies to learn about pathways to desired outcomes; (4) policy studies to respond to information needs in areas of emerging policy-relevant issues; and (5) continuous program improvement. The study involved 3,001 children and families in 17 sites representing diverse program models, racial/ethnic makeup, urban-rural location, program auspice, and program experience in serving infants and toddlers. Three phases comprise the collection: Birth to Three ("0-3"), Pre-Kindergarten ("PreK") Follow-up and Elementary School ("G5") Follow-up. A brief description of each phase is provided below: Birth to Three Phase (1996-2001): included a cross-site national study that encompassed an Impact Evaluation and Implementation Study that investigated program impacts on children and families through their time in the program as well as site-specific research conducted by local research projects. Pre-Kindergarten Follow-up Phase (2001-2005) : built upon the earlier research and followed the children and families who were in the original study from the time they left the Early Head Start program until they entered kindergarten. It was designed to document the long-term consequences of receiving either Early Head Start services or other community services up until age 3 combined with subsequent Head Start or other formal early care and education programs on children's school readiness and parent functioning. Elementary School Follow-up Phase (2005-2010): assessed children and families when the children were fifth graders or attending their sixth year of formal schooling. The study included direct assessments of children's cognitive, socio-emotional, and physical development; parent interviews; teacher questionnaires; and videotaping of maternal-child interactions.