BRCA1 and BRCA2 genes are responsible for 5-10% of breast and ovarian cancer cases. However, the vast majority of ovarian and breast cancer cases do not display the hereditary form of the disease. Estrogen-metabolizing genes may also contribute to the predisposition of breast or ovarian cancer. Polymorphic variants of the estrogen-metabolizing gene, CYP17, have been associated with the risk of hormone-related cancers. In this study we investigated the CYP17 polymorphisms in ovarian cancer patients harboring mutations in the BRCA1 and BRCA2 genes, patients displaying familial characteristics but not carrying mutations and patients with sporadic ovarian cancer. Association between the allele frequencies, the CYP17 genotype and tumor characteristics or clinical parameters was evaluated. Our data suggest evidence for an association between ovarian cancer risk and the CYP17 genotype in the subgroup of patients with familial disease in whom no mutations in the BRCA genes are found. Although there were no statistically significant differences in the genotype distribution between the control group and the subgroup of patients with BRCA mutations, the frequency of the CYP17 A2 allele was significantly higher in the subgroup of patients without BRCA mutations. We found a four- to eightfold higher risk in ovarian cancer patients with family history but without BRCA mutations. Our data indicate that the CYP17 A2 allele polymorphism may confer an increased risk and can provide a biomarker for ovarian cancer patients in whom no mutations in the BRCA genes are observed.