One-hundred-forty-one Blacks (135 unrelated) from Kenya and Tanzania have been tissue-typed (HLA-A, B and C loci) as part of a study of host factors involved in Burkitt's lymphoma and naso-pharyngeal carcinoma. Evidence is presented for the existence in this population of several B15-related antigens which together occur with a relatively high frequency of 30% in unrelated individuals. It is likely that these variants may include the antigens SV and perhaps Bu recently defined with population frequencies of under 1% in Caucasians. In the absence of monospecific typing sera, identification of these variants may be helped by their apparently strong association with C-locus antigens in Blacks. Recognition of these B15 variants has been largely responsible for reducing the proportion of unidentified or "blank" B-locus antigens in this population to only 6%. These findings substantiate and amplify previous reports suspecting the presence of such antigens in Blacks, and should facilitate studies of possible associations of disease with HLA in these populations.