To determine the continuing impact of Head Start experience, this follow-up study compared (1) the behavior of children who had Full Year Head Start (FYHS) experience under three different types of agencies, and (2) within each agency, where possible, the behavior of children who did not have FYHS experience. Subjects were 102 FYHS children and 39 non Head Start children. Data were gathered to assess the child's home background as well as his current school environment. A pretest and posttest battery of four instruments was administered to each child and five sets of observations were made in classrooms where subjects were enrolled. Results indicate that children attended markedly contrasting first year of primary school programs. Changes in intellectual functioning were complex and for the most part inconclusive. Difficulties in research design reflected problems consistent with comparative studies of this type. Rather than conclude that FYHS failed to affect a lasting change in children, this study points up the importance of carefully describing the different classroom environments and selecting appropriate comparison groups when attempting to evaluate the long-range effects of Head Start. Numerous tables are included. (WY)