Selective estrogen receptor modulators (SERMs) are compounds that display mixed 
estrogen agonist/antagonist activity. Currently, four SERMs are licensed for 
clinical use: tamoxifen, toremifene, clomifene and raloxifene. The STAR and RUTH 
trials have provided useful data about the potential role of SERMs in the 
primary prevention of breast cancer and cardiovascular disease in postmenopausal 
women. New-generation SERMs, such as bazedoxifene, arzoxifene, lasofoxifene and 
ospemifene, are currently being evaluated. The aim is to find a SERM that 
conserves the skeleton and prevents breast cancer without increasing the risk of 
endometrial cancer and venous thromboembolism, and without inducing hot flushes. 
Technological advances in the study of estrogen receptor activation will provide 
key information for drug development.