Rural migration is the migration of people from rural areas into cities. The movement of people from rural communities into cities is considered to be the main cause of urban growth, especially in developing countries. Rural migrants are attracted by the possibilities that cities can offer, but often settle in shanty towns and experience extreme poverty.

In cities of the developed world in-migration is another important factor causing city growth. In-migration refers to migration from former colonies and similar places. The fact that many immigrants settle in impoverished city centres led to the notion of the "peripherilazation of the core", which simply describes that people who used to be at the periphery of the former empires now live right in the centre.

Recent developments, such as inner-city redevelopment schemes, mean that new arrivals in cities no longer necessarily settle in the centre. It has been argued that this was never the norm, because settlement pattern differ a great deal between cities.

In some developed regions, the reverse effect has occurred, with cities losing population to rural areas, and is particularly common for richer families. This has been possible because of improved communications, and has been caused by factors such as the fear of crime and poor urban environments. Originally termed "white flight", the effect is not restricted to cities with a high ethnic minority population.