Pure osteosarcomas, in which this tumor is not the mesenchymal component of a biphasic tumor, are only rarely encountered in the ovary. Herein, we report a case of a pure ovarian osteoarcoma and review all previously reported cases of ovarian involvement by osteosarcoma in the English literature. The latter includes (with the present case) 6 cases of pure osteosarcoma (Group A), 5 cases of osteosarcoma arising from a teratoma (Group B), and 2 cases of osteosarcomas of osseous origin (humerus and maxilla) metastatic to the ovary (Group C). The average ages of the Groups A, B, and C patients were 52.6, 52, and 37.5 years, respectively. The average tumor sizes in these groups were 13.46, 13.82, and 16 cm, respectively. There was no statististically significant difference between the Group A and B patients with respect to tumor size (P = 0.94) or age (P = 0.96) (t test). Eight of the 11 patients in groups A and B were FIGO stage 3 or 4 at presentation. Five (83%) of the 6 group A patients and 2 (40%) of the 5 group B patients died of their disease an average of 4.8 and 3.5 months after initial evaluations respectively. However, the 2 patients who presented with stage 1 disease (and with follow-up information) have shown no evidence of tumor recurrence at an average of 26 months' follow-up. It is concluded that ovarian osteosarcomas are rare malignancies that are frequently associated with teratomas but may be seen in pure form. Unlike osseous osteosarcoma whose peak age of incidence is in the second decade, ovarian osteosarcomas occur at an older age group. Most patients have advanced stage disease at presentation. Ovarian osteosarcomas have a high (>60%) case fatality rate; analysis of the reported cases suggests that the latter is attributable to the advanced stage at which most patients present, as there are no reported cases of patients with stage 1 disease whose diseases have recurred after surgical resection or who have died of their disease.