Specimens from 53% (16 of 30) of patients with untreated ovarian epithelial cancers between October 1976 and February 1979 had estrogen binding levels greater than 30 fmoles/mg of cytosol protein (receptor rich). The likelihood of a specimen being receptor rich appeared to be independent of patient age, histologic grade of tumor, clinical stage, and amount of residual tumor left after surgery. For 20 patients with previously untreated advanced disease a life-table analysis showed no significant difference when receptorrich and -poor groups were compared in terms of either survival or time to first progression of disease. Analysis of more recent specimens (predominantly obtained after February 1979) indicates high-affinity binding of the estrogen consistent with receptor; occasional substantial heterogeneity in estrogen binding results between different sites of tumor involvement; and progestin-specific binding in some specimens. In an analogy to breast cancer, patients whose tumors are cytosol estrogen receptor rich might theoretically be responsive to the administration of antiestrogens.