A wide range of profound socio-economic consequences is associated with the global shift in the distribution of population to urban from rural places. Urban growth is adding large annual increases to the population of towns and cities in many countries that are struggling to cope with its consequences. Major problems of employment, housing, service provision and health result. These are widespread across the developing world, but are most acute in those parts of Africa and Asia in which the scale and pace of contemporary urban change are greatest. The inability of many cities fully to accommodate the increase in population by providing work, housing and services points to a situation of overurbanisation which has important consequences for the quality of life and social stability.