Part I of this paper provides an overview of patterns of juvenile offending, with a focus on the small group of offenders responsible for the majority of offenses. Part II examines the problems and characteristics of juveniles that place them at risk of offending. The most recent and reliable research on the issue is reviewed to identify the profiles of juveniles who should be selected for intervention to prevent the evolution of a criminal career. Part III considers what impact, if any, the nature of case processing may have on offending, including the way police deal with juveniles, the effects of various sentences, the use of innovative approaches such as family group conferences, and the combination of processing and other intervention. Part IV, the largest section of the paper, identifies effective responses to juvenile offending. One section provides an overview of current research on interventions that reduce reoffending. This is followed by discussions of specific interventions, including effective approaches in residential and nonresidential settings, the importance of working with the families of juvenile offenders, programs for aggressive and violent juveniles, drug programs, support after intervention, and characteristics of effective staff. There is also an overview of what research has found does not work in reducing juvenile reoffending. Part IV concludes with summary tables of "what works" generally and in each specific area, as well as "what doesn't work." A table also portrays effective approaches for each of the main risk factors identified in Part II. A 102-item bibliography