Current advances in the treatment of malignant diseases by chemotherapy and radiotherapy are saving an increasing numbers of lives. However, cancer treatment can cause changes in sex hormone production, premature ovarian failure and infertility. As survival rates for young girls and women of reproductive age improve, protection against iatrogenic infertility assumes a higher priority. GnRH administration prior to chemotherapy or transposition of the ovaries prior to radiotherapy might reduce ovarian follicular damage. Embryo cryopreservation is an established technique that is available for fertility preservation, providing a delay in the initiation of treatment and the patient has a partner. Cryopreservation of oocytes after ovarian stimulation is another approach for single women. For many adulthood cancers, however, treatment start shortly after diagnosis, not allowing enough time for ovarian stimulation. In children, ovarian stimulation for oocyte and embryo cryopreservation is not considered ethical. Banking of ovarian tissue is a promising option to preserve ovarian endocrine function in young girls and women risking ovarian failure as a result of medical treatment. Once the ovarian tissue is cryopreserved, future options include transplantation of the tissue back to the donor (autotransplantation) or to nude mice (xenotransplantation), or to culture the follicles in vitro. The first child following ortotop transplantation was born in Belgium in 2004.