Only 69% (42 of 61) of the documented ovarian tumor specimens received between September 1981 and August 1982 contained 75% or more viable tumor. Of the 42 measured for estrogen receptors (ER) and progesterone receptors (PR), 34 (81%) had estrogen-binding titers. greater than or equal to I fmol/mg of cytosol protein, while 18 (43%) had progesterone-binding titers greater than or equal to 5 fmol/mg of cytosol protein. ER and PR titers were found to be independent of histologic grade, clinical stage, patient age, age at first pregnancy, age at menarche, age at menopause and number of pregnancies. The presence of ER and PR in malignant ovarian tumors suggests that assays positive for these hormones could aid in the selection of patients suitable for hormonal therapy.