Tibolone is a synthetic steroid hormone selective estrogen receptor modulator (SERM) that acts as an agonist or antagonist depending on the tissue location. Tibolone exhibits anti-osteoporotic, vasodilatory, and anti-metastatic activities. Tibolone has estrogenic and androgenic activity and is used for hormone replacement therapy, preventing bone loss in postmenopausal women; it acts as an agonist at progesterone and androgen receptors. Tibolone and its various metabolites act on many enzymes; they inhibit STS, 17β-HSD1, and aromatase, and activate steroid sulfotransferase and 17β-HSD2. Tibolone produces vascular relaxation in coronary arteries as well. Additionally, this compound inhibits mammary carcinoma cell invasion, likely by decreasing activity of MMP9. Tibolone is an antagonist at mineralocorticoid and glucocorticoid receptors.