In this review, we will present clinical and experimental data that the surface epithelial cells of the ovary are the most likely cell of origin of ovarian cancer. Using a rat model of the disease, we demonstrate the utility of the molecular techniques of Differential Display Genome Scanning and Suppression Subtractive Hybridization to detect gene expression and genetic differences between normal rat surface epithelial cells and their transformed counterpart. Lastly, we provide examples of how molecular techniques can be used to predict which tumors will respond to chemotherapy.