This chapter concentrates on recent robust advances that are likely to affect clinical care over the short to medium term. It discusses potential biomarkers for stratified treatment of high-grade serous (HGSOC) and their relationship with platinum sensitivity and resistance. The accurate diagnosis of sub-type before chemotherapy treatment is vital as it provides strong prognostic and biological information. Many expression microarray studies have attempted to define prognostic and predictive signatures for chemoresistance in epithelial ovarian cancer (EOC). DNA copy number analysis has also been investigated as a predictive marker. Ultrasound- or computed tomography (CT)-guided biopsy is the standard of care for initial diagnosis of women with suspected ovarian cancer. Intratumoral genetic heterogeneity in HGSOC has been demonstrated both within a region of tumour and between different metastatic sites. These genetic differences could be expected to alter chemosensitivity.