OBJECTIVE New regimens and routes of administration of hormonal replacement therapy (HRT) in climateric women are becoming available. Since there is no information on the neuroendocrine effects of sequential combined treatment with 17 beta-estradiol and a progestin, the present study evaluated the neuroendocrine, clinical vasomotor and psychological changes before and after different sequential combined HRT regimens (17 beta-estradiol plus nomegestrol acetate, or cyproterone acetate, or vaginal progesterone). Vasomotor and behavioral effects were evaluated by using the Kupperman score, while changes in plasma endorphin (beta-END) levels were used as marker of neuroendocrine effects. METHODS Postmenopausal women (n = 30) were randomly divided into three groups (ten women for each group); all women received continuous 17 beta-estradiol (50 mg, transdermal) and each group was sequentially treated with different progestins for 12 days/month: group A, cyproterone acetate (5 mg p.o.); group B, nomegestrol acetate (5 mg p.o.); and group C, progesterone (100 mg, vaginal cream). A group of healthy fertile women (n = 8) served as control. Before and after 6 months of HRT, postmenopausal women underwent an evaluation of subjective Kupperman score and two neuroendocrine tests: (a) naloxone (4 mg i.v.) and (b) clonidine (1.25 mg i.v.). Plasma beta-END levels were measured before and at 15, 30, 45, 60 and 90 min after drug injection. Control women were studied by administering the two neuroendocrine tests only once. RESULTS Postmenopausal women before HRT showed a pathological Kupperman and no changes of plasma beta-END levels in response to the clonidine and naloxone tests score. On the contrary the increase was significant in healthy women. In each of the three groups of treated women both naloxone and clonidine tests induced a significant increase in plasma beta-END levels (P < 0.01). After 6 months of HRT, an improvement of vasomotor and psychological symptoms was shown by a decrease of Kupperman score. CONCLUSIONS The present study indicates that sequential treatment with transdermal 17 beta-estradiol and progestin, no matter which progestin was used, restores the beta-END release, improves vasomotor and psychological symptoms.