Epidemiological studies have indicated a relationship between ovarian cancer and gonadal steroid hormones. In the present study immunohistochemical localization in combination with morphometry were used to characterize changes in the pattern of expression for estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta), and progesterone receptor (PR), in epithelial cells of normal ovaries, and in benign, borderline and malignant ovarian tumors of different types (n=53). Positive correlations with immunoreactivity of the cell proliferation-marker, Ki67, and the apoptosis-related marker of genetic instability, p53, between the different tumor types were also found. A simultaneous expression of ERalpha, ERbeta and PR in epithelial cells of all histopathological tumor types was noted, with the notable exception of all mucinous tumors who remained ERbeta-positive, but ERalpha- and PR-negative. Epithelial cells in ovarian cancer tissue showed significantly lower mean immunoreactivity of ERbeta and PR, but not ERalpha, than in normal ovarian tissue. These novel findings may provide a rationale for the development of new diagnostic and possibly therapeutic strategies.