The prevalence of gout and the frequency distribution of serum uric acid (SUA) concentrations have been studied in four South African populations. Approximately 450 respondents over the age of 15 years were investigated in each of the following: a tribal Xhosa community in Transkei; a rural Tswana community in the northwestern Transvaal; an urban Negro population in Johannesburg; and a Caucasian community in the same city. No case of gout was encountered in any of the Negro groups, while the prevalence among the urban Caucasians was 13/1 000 men and 3/1 000 women. The mean SUA concentrations showed two consistent trends: (i) the levels rose with age in all four populations and in both sexes; (ii) they were generally higher in men than in women throughout the age range. There was, moreover, an increase in SUA concentrations with increasing sophistication of lifestyle (P less than 0,01), the lowest levels occurring in the tribal Africans, and the highest in the urban communities. This latter finding could not be explained on a genetic basis, nor were there significant differences in physical configuration and nutritional status among the three Negro groups. It is suggested that hyperuricaemia, and possibly the clinical manifestations of gout, have a polygenic aetiology in which acculturation plays an important contributory role.