Specific estradiol (ER) and progesterone receptors (PR) in the tumor cytosol of 54 patients with primary ovarian cancer were examined. Also 30 benign ovarian neoplasms and 19 normal ovaries were analysed. Of the malignant tumors, 46% contained ER and 41% PR. The ER content of most malignant tumors was 3-30 fmoles/mg protein; three tumors revealed an ER content over 30 fmoles/mg protein. The PR content of most malignant tumors was 8-80 fmoles/mg protein. Three endometrioid adenocarcinomas and three serous cystadenocarcinomas had a PR level over 100 fmoles/mg protein. ER and PR were simultaneously detected in 26% of the malignancies, whereas 39% of them were receptor negative. No significant differences were found between premenopausal and postmenopausal women, as regards the presence of steroid receptors. Carcinomas were significantly more often ER-positive than were benign tumors. The ER content of both the benign neoplasms and the normal ovary was low, less than or equal to 15 fmoles/mg protein, whereas higher PR levels were found in these two groups. The presence of steroid receptors in malignant ovarian tumors can possibly be used as an indicator of hormone dependency of these malignancies.