The importance of BRCA1 and BRCA2 genes stems from the fact that they are 'caretaker' cancer-susceptibility genes, which encode molecules that act as sensors of DNA defects and participate in the repair process. The main function of BRCA2 is its role in HR-mediated DNA DSB repair through its direct interaction with RAD51. Most ovarian cancers occur sporadically, although approximately 10% of patients report an associated family history of the disease. In unselected series, about 6-15% of ovarian cancers have been found to be due to BRCA mutations. The ability to predict an individual's cancer risk accurately is limited by the influence of factors other than whether a BRCA1 or BRCA2 mutation has been inherited. The demonstration of single-agent anti-tumour activity and the wide therapeutic index of PARP inhibitors in BRCA1 and BRCA2 mutation carriers with advanced ovarian and breast cancers provide strong evidence for the clinical application of this approach.