Members of the so-called coloured population are incarcerated at a rate almost double that of their black compatriots, says the South African Institute of Race Relations (SAIRR).
Evidence suggested the higher prison rate could be attributed to the prevalence of gangsterism and alcohol and drug abuse among this group, the institute said in a statement yesterday.
"In October 2007 about 80 percent of South Africa's prison population was made up of Africans, who also made up 79 percent of the entire South African population.
"But the coloured population was incarcerated at a rate of almost 651 per 100000 people.
This was almost twice the imprisonment rate of the African population, which was 342 per 100000 people in 2007.
"White and Indian populations were incarcerated at the same rate of around 60 per 100000 people."
The SAIRR said its analysis of prison populations - published in the 2007-08 edition of its South Africa Survey - was based on figures from the department of correctional services.
"This analysis does not seek to suggest, by any means, that some population groups are more criminally inclined than others.
"Rather, it seeks to identify peculiar environmental influences that might drive members of some communities to criminal activity."
Research had shown that some population groups, such as Indians and whites, had a greater proportion of stable families.
Certain communities, such as those of the Limpopo region, had better social cohesion than others.
"Furthermore, there was evidence that criminal gang activity and drug and alcohol abuse were more prevalent among communities populated by coloured people than others." - Sapa