This study documented that nearly half of a large national sample of Head Start and Early Head Start children enrolled in participating programs experienced adversity and that this adversity is related to their learning and development. However, children in the programs, including those who had experienced adversity, had better outcomes in some domains if they had longer durations in their early childhood programs. Implications of these findings include the need to a) understand the experiences of the children and families in Head Start as part of preventing and reducing adversity; b) address the effects of adversity in instructional and other interventions to promote children's learning and development; and c) work to retain high risk families through targeted programming and professional development. (author abstract)