Tamoxifen citrate is an orally administered, nonsteroidal antiestrogen agent that is widely used for the treatment of breast cancer and that has recently been found to prevent breast cancer in some high-risk populations. Tamoxifen may, however, cause adverse effects at the uterine level. In this article, the authors review (a) the histopathologic uterine changes associated with tamoxifen therapy, (b) the spectrum of uterine imaging findings in women treated with tamoxifen, and (c) the recommendations of the American College of Obstetrics and Gynecology for women treated with tamoxifen. An algorithm for imaging evaluation of the uterus in women treated with tamoxifen is presented.