The main purpose of the hearing reported in this document was to expand the knowledge of the Select Committee on Children, Youth, and Families concerning early intervention at several critical points during infancy, early childhood and early and later adolescence. Six distinguished researchers in child development gave testimony at the hearings and also submitted prepared statements. The focus of the testimony was to present state-of-the-art findings about how to prevent damage to children and how to ensure their well being. The research experts testified on those areas where consensus of research is clear, and where public policy should reflect that consensus. They also pointed out issues regarding childhood and adolescence that require further research before a consensus can be reached. Findings of a recent study which compared the U.S. record on infant mortality and morbidity and preventive measures with the record of 10 Western European countries are included, as are the findings of the American Psychological Association's Task Force on Promotion, Prevention and Intervention Alternatives whose mission was to identify successful prevention models and programs where evidence of effectiveness was convincing. (RWB)