In order to assess the effects and acceptability of transdermal estradiol on the prevention of the loss of bone mass, the Authors administered transdermal estradiol (ETTS 50 mcgr/day) for 3 weeks and, cyclically, medroxyprogesterone 10/mg/day from day 10 to day 21 of each cycle for 12 months, to 20 operated patients for bilateral ovariectomy. Primary markers of the bone turnover (hydroxyproline urinary, osteocalcin, PTH) were estimated before therapy and after 3, 6, 9, 12 months. The BMD was evaluated before therapy and after 6 and 12 months. Our study clearly shows that the transdermal administration of estradiol prevents the postmenopausal bone loss, also in postmenopausal women at higher risk of developing osteoporosis as those evaluated in our study.