Ovarian cancer is the most common cause of death among gynaecological cancers in women as per the Madras Metropolitan Tumour Registry. Around 5% of the ovarian cancers have a hereditary background. The important genes linked to epithelial ovarian cancers include BRCA1, BRCA2, MSH2, and MLH1. p53 gene deleterious mutation can lead to Li Fraumeni syndrome wherein germ cell tumours of the ovary can occur. Mutations in STK11 gene (Peutz Jeghers syndrome) can predispose to sex cord tumours and Sertoli-Leydig cell tumours of the ovary. Hereditary cancers particularly due to BRCA1, 2, MSH2 and MLH1 offer the potential for risk reduction strategies and hence cancer prevention in women who carry the deleterious mutants. This chapter also briefly presents data on some of the oncogenes and tumour suppressor, genes associated with ovarian cancers.