Blood sera of 181 women with inflammatory conditions and with benign and malignant neoplasms of the ovary and of 36 healthy women (control group) were examined by determining the levels of defense proteins: C-reactive protein (CRP), alpha 1 antitrypsin (A1AT), alpha 2 macroglobulin (A2M), components C3 (beta 1 A-globulin) and C4 (beta 1 E-globulin) of the complement, immunoglobulins M (IgM), A (IgA), and G (IgG), as well as the concentration of circulating immune complexes (IC). In women with ovarian pathology, as compared with the control group, a significant increase of all the defense proteins was found (p less than 0.05). The highest increase of the defense proteins, except in regard to A2M was observed in inflammation of the ovary. In malignant neoplasms of the ovary, the level of A2M was the highest and that of A1AT as high as in inflammatory conditions. There was also a high percentage of increased CRP values (57%). The concentration of the remaining proteins under study, although significantly higher than in the control group (p less than 0.05), was in this group the lowest in comparison with the groups of ovarian inflammation and benign neoplasms, especially with regard to component C3 of the complement and to IgM and IgG (p less than 0.05). Significantly increased values of IC (p less than 0.05) were observed in ovarian inflammation (73.2%) and in benign neoplasms (25.0%). In the group of malignant neoplasms (15.4%) and in healthy women (5.6%), the increased IC values were not statistically significant (p less than 0.05).