A family history of ovarian cancer confers an increased risk of ovarian cancer. We review the literature quantifying the familial risks associated with ovarian cancer and assess the evidence that the familial clustering of ovarian cancer is genetically determined. We then describe the known high-penetrance genes, the ovarian cancer risks attached to them and their contribution to ovarian cancer in families and in the general population. The evidence for the existence of other ovarian cancer genes is then considered.