Abstract Objectives: Presentation of a group of patients with diagnosed malignant ovarian germ cell tumors (MOGCT), determination of prognostic factors and outcome analysis. Material and methods: We selected patients with diagnosed malignant ovarian germ cell tumors from the patient registry of Cancer Center in Warsaw from 1990 to 2001. We analyzed clinical and pathological features of the study group, as well as methods and results of treatment. Results: We collected documentation of 83 patients. Most were diagnosed with dysgerminoma and immature teratoma in the early stages of development. 73 patients received adjuvant chemotherapy after surgery. At the end of the first line of treatment complete response was achieved in 63 patients (75.9%). Time to recurrence ranged from 25 to 518 days (mean 176 days). The most common site of recurrence was the true pelvis. The five-year overall survival was 62.7%. Significant favorable prognostic factor was early stage of disease and the histological diagnosis of dysgerminoma. From the 46 women after fertility-sparing surgery, 8 became pregnant. Conclusions: MOGCT are a group of potentially curable, yet very aggressive malignant ovarian tumors. The main condition for obtaining good results is quick diagnosis and appropriate treatment, usually surgery associated with multidrug chemotherapy. The stage of the disease remains the most important prognostic factor. Patients diagnosed with dysgerminoma are a separate group with very good prognosis.