Ovarian cancer continues to be the foremost cause of mortality because of gynecologic malignancies. Surgical and chemotherapeutic advances have been made, yet the cause of ovarian oncogenesis is poorly understood. Recognition of the familial clustering has focused investigators in the direction of isolating genetic susceptibility loci for ovarian cancer. Research on cytogenetic abnormalities have led to the identification of oncogenes and tumor suppressor genes, which have contributed to a multistep model of molecular oncogenesis. This review discusses how the familial clustering of breast and ovarian cancers, as well as the chromosomal alterations and oncogenes identified, have all contributed to our understanding of the genetic factors involved in the development of ovarian cancer.