The objective of the study was to observe the effects of hormone replacement therapy upon urinary prostaglandin E-2 and prostaglandin F-2 alpha levels in postmenopausal patients. A total number of 55 women were enrolled in this study and 15 premenopausal (PreM) healthy subjects constitute the control group. A total of 40 patients at least 12 months after their natural menopause were divided into two groups: 15 of them was not medicated hormone replacement therapy (which composed NRHRT group) while 25 of the rest, received conjugated estrogen (Premarin) 0.625 mg/day orally plus medroxyprogesterone acetate (Farlutal) 10 mg/day orally built up the RHRT group. PGE(2) and PGF(2 alpha) levels were measured with PGE(2) [I-125] and PGF(2 alpha) [H-3] RIA kits. Statistical significance was analyzed by Student's t-test for impaired data. NRHRT and RHRT patients had had increased urinary PGE(2) levels when compared with PreM (P < 0.001). HRT caused a significant decrease in PGE(2) levels in menopausal women (P < 0.001). Urinary PGF(2 alpha) values of NRHRT and RHRT were significantly lower (P < 0.001) in comparison with PreM group. There was no difference in PGF(2 alpha) values between two postmenopausal groups. HRT given to postmenopausal patients might have a positive impact on prostaglandins and therefore on bone turnover in a series of various mechanisms. (C) 1998 Elsevier Science Ireland Ltd. Ail rights reserved.