Ovarian carcinomas were formerly referred to as "surface epithelial carcinomas," reflecting the belief that they all arise from the ovarian surface epithelium. It is now appreciated that most ovarian carcinomas originate from either fallopian tube or endometriotic epithelium, and how we approach prevention will thus differ between histotypes. The 5 histotypes of ovarian carcinoma (high-grade serous, clear cell, endometrioid, mucinous, and low-grade serous, in descending order of frequency) can be reproducibly diagnosed, and are distinct disease entities, differing with respect to genetic risk factors, molecular events during oncogenesis, patterns of spread, and response to chemotherapy.