comprehensive scheme to redress a complex of urban (urbanization) problems, including unsanitary, deficient, or obsolete housing; inadequate transportation, sanitation, and other services and facilities; haphazard land use; traffic congestion; and the sociological correlates of urban decay, such as crime. Early efforts usually focused on housing reform and sanitary and public-health measures, followed by growing emphasis on slum clearance and the relocation of population and industry from congested areas to less-crowded sites, as in the garden-city and new-towns movements in Great Britain. Late 20th-century criticisms of urban sprawl prompted new interest in the efficiencies of urban centralization.

Each country approaches urban renewal according to its means and its political and administrative systems. One of the chief activities of urban renewal is redevelopment, which is achieved through the clearance and rebuilding of structures that are deteriorated or obsolete in themselves or are laid out in an unsatisfactory way. Other aspects of urban renewal involve the reuse of the land for new purposes, rehabilitation of structurally sound buildings that have deteriorated or lost their original functions, and conservation—a protective process designed to maintain the function and quality of an area, for instance, by requiring or assisting adequate maintenance while preventing inappropriate development or uncharacteristic changes in the use of land and buildings.