The number of cities in South Korea was 15 in 1945, and 13 percent of the population resided in them. By 1966 the number of cities had increased to 32, and 28 percent of the population lived in them. This increasing urban concentration was due primarily to Korean war refugees' concentration in large cities and population migration from rural to urban areas on a large scale. This migration into the cities occurred abruptly without any preparation for the expansion of basic facilities. Rapid urbanization continued in the 1970's with the progress of industrialization. In the latter half of the 1980's, crimes became significantly more violent. Distinctive cultural characteristics, however, have kept urban crime from becoming as serious as in advanced Western nations. Factors that have controlled crime are the maintenance of ethnic homogeneity, a relatively strong government, enthusiasm for higher education, and the legal prohibition and unavailability of deadly weapons. The proportion of juvenile offenders (14-19 years old) remained between 12 and 18 percent during the 1980's and in 1991 was 12.4 percent. The social and environmental changes have affected the character and attitudes of juveniles, brought changes in the family environment, fostered school problems, contributed to the juvenile gang problem, and fueled the victimization of juveniles by other juveniles. Efforts to counter juvenile delinquency include the restoration of moral principles and social order, the efforts of neighborhood residents to reduce criminogenic environmental factors, and improved operations of juvenile justice through community-based rehabilitative programs. 2 tables