Steroid receptors were measured in 31 malignant and 29 benign or semimalignant ovarian tumors in a prospective study. Estrogen receptors (ER) were found more often in highly differentiated malignant tumors (86%) than in poorly differentiated ones (23%). No such difference was found for progesterone receptor (PR). Receptor content was not related to clinical stage. The median survival of patients with PR+ or ER+/PR+ malignant tumors was 30 and 31.5 months, respectively, compared to 10 and 9 months for those with receptor negative tumors. This positive prognostic information could not be demonstrated for ER alone. Receptor content and distribution were similar in benign and semimalignant tumors. Measurement of hormone receptors in ovarian cancers can thus give valuable prognostic information.