Yolk sac tumor (YST) occurs rarely in older women, either in association with a variety of ovarian epithelial tumors or, considerably less often, without an identifiable epithelial precursor. The patients often have elevated serum levels of α-fetoprotein that roughly correlate with the amount of the YST component. In postmenopausal women with an ovarian mass and elevated serum levels of α-fetoprotein, a tumor of this type should be suspected. Endometrioid carcinoma is the most common putative precursor, and the tumor is often associated with an endometriotic cyst; however, malignant Müllerian mixed tumor and mucinous neoplasms have also been reported as precursors. We report 4 cases of YST in postmenopausal women. Of the 3 cases with an identified epithelial component, 1 was serous carcinoma, another was clear cell adenocarcinoma, and the third was an admixture of endometrioid and clear cell adenocarcinoma arising from an endometriotic cyst. Although a precursor epithelial ovarian neoplasm, typically a malignancy (somatic carcinoma), is usually identified, no precursor neoplasm was observed in 1 of our cases and in 5 cases from the literature. We believe that YSTs in older women, whether or not an epithelial component is detected histologically, constitute a single entity that is distinct from YSTs in younger patients and should be treated aggressively. Neoplasms with a YST component in older women are less responsive to the chemotherapy currently used for ovarian germ cell tumors; therefore, adjuvant therapy should include platinum-based chemotherapy designed to treat both epithelial ovarian cancer and germ cell tumors. Of the 24 reported cases, including our own, 17 died of neoplasms within 25 months and another was living with disease at 2 months. However, 2 more recent patients treated aggressively with platinum-based chemotherapy designed to treat both epithelial and germ cell tumor components with stage 1 disease are living and have been disease free >1 year after operation.