The high incidence of rheumatic heart disease (RHD) in black South African children has been attributed mainly to poor socio-economic status and over-crowding. In order to elucidate whether other factors, in particular genetic, were responsible, the HLA-status of 61 black children with rheumatic heart disease was compared with that of 1165 normal controls. Overall, no differences were found, except a higher incidence of HLA-B25 and BW51 in the group with rheumatic heart disease, when the difference was not of statistical significance. Moreover, when the patients were considered in two groups, viz. (a) a "surgical" group which required cardiac surgery and (b) a "non-surgical" group in which cardiac failure was absent or could be easily controlled by medical therapy, the difference between the two groups was also not of statistical significance, though there was a higher incidence of HLA-A10 (which includes HLA-A25 and A26) in the "non-surgical" group. These data appear to agree with the results of other studies which found no significant association between HLA-status and RHD.