This report summarizes the results of a study on the impact of Head Start on children's cognitive and socioemotional development, on child health and health institutions in the community, on enrollees' families, and on communities where Head Start programs operate. After discussing the background and methodology of the study, the report concludes that children enrolled in Head Start enjoy significant immediate gains in cognitive test scores, socioemotional text scores, and health status. In the long run, however, cognitive and socioemotional test scores of former Head Start students did not remain superior to those of disadvantaged children who did not attend Head Start. A small subset of studies did find that former Head Start students were more likely to be promoted to the next grade and were less likely to be assigned to special education classes than their peers. Head Start has also aided families and communities by providing health, social, and educational services to families and by linking families with services available in the community. (MDM)