The preoperative serum level of tumor marker CA 125 has served as rough orientation in making the distinction between a benign and a malignant adnexal mass or as a reference for monitoring the success of therapy. But there were some reports suggesting that the stage of the disease and tumor grade, which are known to be the independent prognostic factors in ovarian cancer patients, may exert an influence on the preoperative CA 125 level. In this retrospective study we analysed the significance of preoperative serum CA 125 level with respect to tumor grade and tumor stage. Between June, 1989 and January, 1997, 82 patients with epithelial ovarian cancer managed at Asan Medical Center were evaluated, in whom serum level CA 125 were measured preoperatively. Tumor grade bears no meaningful influence on the preoperative CA 125 level, and also the correlation is low and statistically insignificant (r=0.12, p=0.29 in all stages; r=0.01, p=0.97 in stage I; r=-0.09, p=0.83 in stage II; r=0.06, p=0.72 in stage III; r=0.25, p=0.41 in stage IV). There was no significant effect of FIGO stage on preoperative CA 125 level (r=0.21, p=0.06 in all grades; r=0.32, p=0.10 in G1; r=0.08, p=0.74 in G2; r=0.17, p=0.30 in G3). However, we found a significant correlation between FIGO stage and tumor grade (r=0.45, p<0.01). In conclusion, our data suggests that both tumor grade and FIGO stage have no significant effect on preoperative serum CA 125 level.