Improved treatment of breast cancer in premenopausal patients increased survival rates, but the therapy may influence fertility and ovarian function. Currently there is a big public and individual interest of breast cancer affected women in preservation of ovarian function and fertility. Chemotherapy induced amenorrhea (CIA) has many objective (osteoporosis, cardiovascular, urogenital atrophy, cognitive etc.) and subjective (hot flushes, sleep disturbances, change of mood etc.) consequences. In patients with breast cancer who wish to avoid a CIA and to preserve their fertility ovarian protection by GnRH agonists, cryopreservation of operative sampled ovarian tissue or obtained fertilized or non-fertilized eggs after stimulation and puncture or embryos after in vitro fertilization are technically possible. However there are no evidence-based recommendations for preservation of fertility or ovarian function in breast cancer patients. Except the cryopreservation of embryos all other procedures are experimental. It is also undefined who is going to carry the costs. Moreover, there are recent data that the reappearance of ovarian hormones may stimulate occult tumor cells in hormone sensitive breast cancer. Therefore it seems necessary to inform breast cancer patients about the possible negative effects of preservation of ovarian function.