The purpose of this paper is to study the essential characteristics of the contemporary-type juvenile delinquency in relation to its social back-gorunds. First, the author referred to the differences between the traditional and the contemporary types of juvenile delinquency. Secondly, the author pointed out that distinctive tendencies of the contemporary-type juvenile delinquency are "generalization of delinquency" and the increase of "play-type delinquency", and analized the characteristics of each tendency in connection with its social backgrounds. In this paper, the author defines the contemporary-type juvenile delinquency as "the characteristic form of juvenile delinquency in contemporary society and the form of juvenile delinquency which sharply reflects the contemporary social situations". By defining in this manner, it is clear that the form of juvenile delinquency which has the distinction of "generalization" and "play-type" is a tapical form of the contemporary-type juvenile delinquency. But traditional-type juvenile delinquency which is committed by boys with handicaps in their dispositions and/or environments, remains firmly in this society, and the author would like to define much of this type as another contemporary-type juvenile delinquency. Recent tendency of juvenile delinquency is the strong dichotomy between the middle-class, play- and escape-type juvenile delinquency and the traditional, violent- and aggressive-type juvenile delinquency. The author analized this in relation to the duality of contemporary social structures and the social situations of administrated society.
