Mutations in the BRCA and p53 tumor suppressor genes are implicated in the oncogenesis of ovarian tumors although their exact roles remain unclear. Despite recognized ethnic differences in the frequency of ovarian cancer and in genetic polymorphisms between populations, studies carried out so far have focused almost entirely on Caucasian subjects. In this study, undertaken at King Edward VIII Hospital, Durban, South Africa, we examined blood and/or primary epithelial ovarian tumor tissue from 75 black South African women for the presence of the three most commonly occurring BRCA 1 and 2 mutations (185delAG, 5382insC and 6174delT). The p53 codon 72 allele status was also examined and results were compared to a reference cohort comprising 340 ethnically matched subjects. None of the BRCA 1 or 2 mutations were detected in the patient group. The codon 72 Arg allele frequency in lymphocytic DNA was not significantly different compared with the control group. In contrast, in ovarian tumor DNA, the Arg allele was found significantly more frequently than in the controls; this was observed in terms of both Arg allele frequency (45% vs. 31%; P = 0.017) and Arg homozygosity (20% vs. 9%; P = 0.039). Tumors with the more aggressive serous papillary cystadenomatous histology had a markedly higher Arg frequency (45%) than the mucinous cystadenomas (25%). The higher frequency of the Arg allele detected in this study in black South Africans with ovarian tumors suggests a possible role in malignant transformation and may constitute a risk factor for ovarian and other epithelial cancers through mechanisms yet to be elucidated.