On June 24-25, 1999, the Committee on Integrating the Science of Early Childhood Development of the Board on Children, Youth, and Families of the National Research Council/National Academy of Sciences and the Institute of Medicine convened a workshop for researchers and practitioners to examine the underlying knowledge base that informs current best practices in early childhood services, from the prenatal period to school entry. Early Childhood Intervention discusses the diversity of working assumptions, theories of change, and views about child development and early intervention that currently shape a wide variety of social policies and service delivery systems for young children and their families.