Ovarian dysgerminomas are distinguished from other ovarian neoplasms by their rarity, their predilection for metastases via lymphatic pathways, and their radiosensitivity and favorable prognosis. After the initial surgery, which provides the histologic diagnosis and defines the local extent of pelvic involvement, lymphography is the single most useful tool to determine whether retroperitoneal lymph nodes are involved. Results of the study guide the radiotherapeutic approach, including field size and dosage. In an unselected group of 31 previously untreated patients, 10 had positive lymphograms. The response to therapy and the detection of relapse of disease may be evaluated by monitoring the residually opacified lymph nodes with surveillance abdominal radiographs. If necessary, a repeat lymphogram can be performed. The 2 year survival rate of 84% for ovarian dysgerminomas is lower than that for testicular seminomas, probably due to later recognition of the tumor. Failuresare related to local extension or to hematogenous dissemination.