A prospective monocentric open-label and single-arm trial was performed in 19 postmenopausal women with diagnosed vaginal atrophy. The aim was to determine the extent of a systemic exposure to estriol (CAS 50-27-1). Administration of estriol containing pessaries was daily for 21 days. In order to establish a pharmacokinetic profile after single as well as multiple vaginal doses of 0.03 mg estriol blood samples were taken after the first vaginal administration as well as at day 21 after the last administration. Moreover, in order to control for accumulation additional blood samples were taken predose at days 6, 11 and 16.