Urbanization is characterized by high concentration of population in which individuals remain isolated and where informal social controls have become inoperative, heightening opportunities for crime. Ghettoization occurs with the influx of socioeconomically disadvantaged workers, indigents, pensioners, and especially foreigners into decaying inner-city neighborhoods. Overcrowding, substandard sanitary conditions, and lack of playgrounds and parks constitute a deprivational environment with criminogenic implications for children and youths. City planning measures for crime prevention include modernization of outmoded buildings, housing codes with precise space requirements, and accommodation of residents' security, recreation, and socializing needs. Legislation must be passed to achieve these goals. City planners should avoid such crime-generating constellations as locating schools in the proximity of department stores or pleasure quarters and renewing concentrations of socially marginal residents. New housing developments must incorporate leisure facilities, traffic control, common areas, and defensible space with adequate visibility and boundaries between private, communal, and public areas. Townhouses for up to four household units are deemed the optimal arrangement of multifamily housing. Police should provide targeted patrol of high-risk locales and during periods of intensified activity. Planners should be aware that certain improvements may also be conducive to negative phenomena (e.g., a newly established youth center as a locus of gang activity) and coordinate steps to forestall such developments. Footnotes are given.