Epithelial ovarian cancer (EOC) has been associated with oxidative stress (OS) due to epithelial inflammation which makes ovaries more vulnerable to the deleterious effects of reactive oxygen species (ROS). However, antioxidant enzymes (AOEs) such as manganese-superoxide dismutase (Mn-SOD), copper,zinc-superoxide dismutase (Cu,Zn-SOD) and glutathione peroxidase (GPx1) protect cells against the biological damage of ROSinduced OS and support cancer prevention by maintaining normal cell cycle progression, inhibiting proliferation, tumor invasion, angiogenesis, inflammation or inducing apoptosis. In the present study, we aimed to measure the levels of trace elements [manganese (Mn), copper (Cu), zinc (Zn) and selenium (Se)] which are structurally and/or functionally associated with the AOEs by inductively coupled plasma/mass-spectrometry (ICP/MS) in blood samples of patients with EOC (M, n = 26) and compare the data with healthy subjects (C, n = 46). Serous EOC (M1, n = 18) data were also evaluated according to the tumor grading [well or moderately well differentiated (G 1-2) vs. poorly differentiated or undifferentiated (G3)] and staging of disease [stage I-II (SI-II) vs. stage III (SIII)]. We obtained; i) The Mn and Se levels of M were significantly lower than C, ii) only Mn levels were changed [(G30,) < G 1-2 04,01 in Ml, iii) significant correlations were observed between [Cu and Zn levels (r = 0.701, p = 0.036) in G 1-2 and (r = 0.686, p = 0.041) in G3; Cu and Se levels (r = 0.960, p = 0.000) in G3; Mn levels and Mn-SOD expression (r = 0.551, p = 0.006) in M, (r = 0.857, p = 0.007) in G 1-2 and (r = 0.690, p = 0.056) in G3; Se levels and erythrocyte GPx1 activity (r = 0.660, p = 0.053) in G 1-2; Se levels and erythrocyte Cu,Zn-SOD activity (r = 0.693, p = 0.038) in G3]. The study revealed that trace elements, particularly low Mn and Se levels along with high Cu/Se ratios might be of value in all histologic subtypes of EOC. Although Mn level was important in terms of discriminating tumor grades, positive correlation between Cu-Se levels was also remarkable in patients with G 1-2 tumors of Ml. Moreover, high erythrocyte Cu/Se ratios might be a favourable marker for EOC.