This book reports on the High/Scope Perry Preschool Project, a longitudinal study assessing whether high-quality, active learning preschool programs can provide both short- and long-term benefits to children living in poverty and at high risk of failing in school. For almost 3 decades the study has followed the lives of 123 such children from African-American families who lived in the neighborhood of Perry Elementary School in Ypsilanti, Michigan, in the 1960s. Focusing on the age-27 phase of the study, the report is divided into 10 chapters which discuss: (1) preschool program effects; (2) the experiment design; (3) educational performance; (4) delinquency and crime; (5) economic status; (6) family formation, health, and social relations; (7) cost-benefit analysis; (8) a causal model; (9) individual case studies; and (10) the overall study in perspective. Study findings at age 27 as reported in these chapters indicate that the preschool participants have significantly higher earnings, rates of home ownership, and levels of schooling, as well as significantly fewer arrests and social service interventions, than a control group of non-preschool participants. Cost-benefit analysis revealed that, over the lifetimes of the participants, the preschool program returned to the public an estimated $7.16 for every dollar spent. Includes 194 references. A separately published 13-page "summary", based on the content of chapter 10, has been appended. (MDM)