The proposals for delinquency prevention are based upon (1) a 5-year study of the reasons for the delinquent breakdown of 102 youths, (2) a series of controlled studies of juvenile delinquents within the community and the followup of some 700 of them for 10 years into adulthood, and (3) empirical studies of cultures and the effects of cultural disintegration. Also, recent events have afforded natural experiments in how persons react to the removal of constraints. An examination of the present state of knowledge of juvenile delinquency considers delinquents and their family backgrounds and social environments, and testing the theory of the subcultural delinquent. In considering the present state of practice, the focus is on the conflict of philosophies in the disposition of the offender, lessons from some American experiments in prevention, and new developments in Britain. An understanding of delinquent behavior is provided under the topics of delinquent states of mind, maladjustment and normality, and family situations conducive to delinquency. The techniques of prevention and treatment proposed are based on an integration of community and individual casework. In addition to counseling the offender's parents, the social worker should influence the quality of the neighborhood to help make life more bearable for the residents. For the caseworker investigating the motives for the offense of a particular juvenile and his/her family background, diagnostic worksheets are provided. These systematize information on the character of the offense, the juvenile's own justification for it, and the juvenile's behavior in the home and community. About 170 references and a subject index are provided.