Objectives: The assessment of the prognostic value of Ca 125 tumor marker in ovarian cancer patients measured after debulking surgery on the disease free survival. Design: To indicate, that the serum Ca 125 level after debulking surgery has an impact on survival. Material: The subject of retrospective analysis was the group of 465 ovarian cancer patients, clinical stage: IC-III, treated in Gynecological Department of Maria Sklodowska-Curie Memorial Cancer Center and 15 other oncological departments during the year 2001. All patients were treated with initial surgery and adjuvant chemotherapy. Methods: The analysis of the serum Ca 125 tumor marker normalization rate after debulking surgery and its impact on disease free survival was performed. Results: Among the analyzed group of patients, the highest rate of survival was observed in the group of patients with normal Ca 125 serum level after surgery, the statistically worst prognosis was observed in the group without Ca 125 normalization neither after surgery nor after chemotherapy. Conclusions: The normalization rate of Ca 125 serum concentration after initial debulking surgery may be an important prognostic factor.