Anti-estrogen therapies for treating ovarian carcinoma have had mixed outcomes suggesting some tumors may be estrogen-dependent. We assayed the activity levels of 17beta-hydroxysteroid dehydrogenase (17beta-HSD), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD/3-KSR) and estrone sulfatase in a series of ovarian epithelial carcinomas. 17beta-HSD activity ratios with estradiol (E(2)) and testosterone (T), and inhibition by isoform-specific inhibitors were used to estimate the contributions of 17beta-HSD isoforms. Activity levels were highest for estrone sulfatase, followed, respectively by 17beta-HSD, 3alpha-HSD/3-KSR, and 3beta-HSD. E(2)/T activity ratios varied widely between samples. A 17beta-HSD type 1 inhibition pattern was observed in 23% of the samples and a type 2 pattern in 25%. E(2) formation from estrone sulfate (E(1)S) was detected in 98% (47/48) of the samples. 17beta-HSD type 1, type 2 and type 5 mRNA was detected in matched primary tumor and metastases. Evaluation of 17beta-HSD and sulfatase activity levels, activity ratios and inhibition patterns may help predict tumor response to endocrine therapy.