To visualize the heterogeneity of androgen receptor (AR) and progesterone receptor (PR) expression in ovarian tumors, 61 specimens were studied immunohistochemically using specific mouse monoclonal antibodies. The tested ovarian tumors included ovarian carcinomas of serous, mucinous, endometrioid, undifferentiated, and clear cell types as well as borderline epithelial tumors, mucinous cystadenomas, granulosa cell tumors, metastatic ovarian tumors, and one case of immature teratoma. Sixty-seven percent of ovarian carcinomas expressed AR, while 46% of the ovarian carcinomas expressed PR. In addition, the three tested borderline epithelial tumors were AR positive. Androgen receptor and PR were primarily localized in the nuclei of ovarian tumor cells. In three tumors focal staining of intervening stroma cells was observed. Interestingly, 35 of the granulosa cell tumors expressed PR as well as AR. All tumor types displayed a wide range in their proportions of AR- and PR-positive tumor cells. A poor correlation, however, was observed when semiquantitative immunohistochemical AR staining results on 17 ovarian carcinomas were compared with biochemical cytosol AR estimations using the dextran-coated charcoal method. Our study indicates that AR as well as PR is expressed by a substantial proportion of ovarian borderline and malignant tumors and that there is a strong heterogeneity in expression of AR and PR. It is possible to evaluate the prognostic significance of these receptors in ovarian cancers on fresh-frozen tumor specimens using a simple immunohistochemical technique.