Quinestrol has been used as the estrogen component in menopausal hormone therapy and in combined hormonal birth control.[1][2] It has also occasionally been used in the treatment of breast cancer and prostate cancer.[2][3] On its own as an estrogen, quinestrol was taken once per week by mouth.[4] As a combined birth control pill, it was used together with quingestanol acetate and was taken once per month by mouth.[5][6][7]