Preface vii strategy in medical research; it is time for its importance to be appreciated and pursued with new vigor in criminological research.This book makes the case for such research and spells out many of the details by which it could best be pursued. Chapter 1 provides an overview of what we now know about crime and criminals and how we might know more so as to better shape criminal justice policy to our needs. In Chapters 2 and 3, we review in some detail what we have learned from longitudinal and experimental studies in criminology thus far. In Chapters 4 through 7, we explore selected key policy issues to illustrate current deficiencies in the knowledge needed to develop more costeffective action strategies. In these chapters we consider, respectively, families and schools as targets of prevention measures, theories about the effects of labeling, proposals for reorganizing the juvenile courts, and the effects of imprisonment. Finally, in Chapter 8, we discuss possible research designs and strategies we might now pursue to build firmer ground for our criminal justice policies.