Clomifene is a nonsteroidal triphenylethylene derivative that acts as a selective estrogen receptor modulator (SERM). It consists of a racemic mixture of zuclomifene (~38%) and enclomifene (~62%), each of which has unique pharmacologic properties. It is a mixed agonist and antagonist of the estrogen receptor (ER). Clomifene activates the ERα in the setting of low baseline estrogen levels and partially blocks the receptor in the context of high baseline estrogen levels. Conversely, it is an antagonist of the ERβ. Clomifene has antiestrogenic effects in the uterus. There is little clinical research on the influence of clomifene in many target tissues, such as lipids, the cardiovascular system, and the breasts. Positive effects of clomifene on bone have been observed. Clomifene has been found to decrease insulin-like growth factor 1 (IGF-1) levels in women.