The present report of a 25 year old woman with a primary ovarian angiosarcoma is supplemented by histochemical and ultrastructural studies and reviews the literature of this extremely rare neoplasm. Since this ovarian tumor, especially in young women, may constitute a diagnostic pitfall, problems relating to differential diagnosis are emphasized. Although the origin of this neoplasm appears to occur most likely from the rich ovarian vasculature, other less conventional histogenetic theories such as a possible origin in mixed mullerian tumor, in teratoma or in other ovarian germ cell tumors have also been proposed and are considered in this paper.