Two-thirds of South Africa's population now lives in urban areas, according to the most recent survey of the country released by the South African Institute of Race Relations (SAIRR) in Johannesburg on Tuesday.
The data in the survey comes from the World Bank.
"The proportion of people living in urban areas increased from 52% in 1990 to 62% in 2011," the institute said in a statement.
The share of those living in rural areas dropped from 48% to 38% over the same period.
SAIRR identified the major causes of the trend as the post-apartheid freer movement of people and higher economic growth in urban areas, attracting people searching for employment.
"Among other things, urbanisation creates conditions for concentrated economic activity," said SAIRR researcher Thuthukani Ndebele.
"The downsides, however, may be that urbanisation fuels crime and social tensions, creates greater environmental and health risks and poses challenges for government service provision."
The most rapid growth has taken place in South Africa's smaller cities, mostly due to small initial populations and increasing economic activity.
"Polokwane, Rustenburg, Vanderbijlpark, Nelspruit and Ekurhuleni [are] the five fastest-growing urban areas, with average annual population growth rates of between 1.6% and 2.9% over the last decade, compared to Cape Town with a rate of 1.4%," Ndebele said.
"Population growth results from a combination of natural growth - higher fertility and life expectancy - and in-migration."
It is expected that Africa's rate of urbanisation will have overtaken Asia's by 2030.
South Africa's population grew by 15.5%, or almost 7-million people, in the space of 10 years to reach a total of 51.7-million in 2011, according to the country's latest national census, conducted by Statistics South Africa.
Gauteng province, the country's geographically smallest but economically busiest province, has both the biggest and the fastest growing population, according to census 2011, with 12.2-million people counted in 2011 - a 33.7% increase over 2001, more than double the national average increase.