We studied 16 postmenopausal women with mild to moderate hypertension according to a randomized, double-blind protocol. They received patches of transdermal estradiol-17beta rated to deliver 100 mg/day of substance or matched placebo. A 24-hour ambulatory blood pressure (BP) monitoring was performed at baseline and after drug administrations. Our data show that estradiol-17beta exerts beneficial effects, both in lowering elevated BP levels and in maintaining a uniform BP control over 24 hours. Estrogen replacement therapy could be considered when significant changes in BP occur during the postmenopausal period.