In women, ∼10% of cancers occur in those 90% of girls and young women with diseases that require such treatments. However, these treatments can result in premature ovarian failure, depending on the follicular reserve, the age of the patient and the type and dose of drugs used. This article discusses the different fertility preservation strategies: medical therapy before chemotherapy; ovarian transposition; embryo cryopreservation; oocyte vitrification; and ovarian tissue cryopreservation. The indications, results and risks of these options are discussed. Whether medical therapy should be used to protect the gonads during chemotherapy remains a source of debate. Fertility preservation needs to be completed before chemotherapy and/or irradiation is started and might take 2-3 weeks with established techniques such as embryo or oocyte cryopreservation. Further studies are needed in patients with cancer to confirm the excellent outcomes obtained in patients without cancer or in egg donation programmes. For prepubertal girls or cases where immediate therapy is required, cryopreservation of ovarian tissue is the only available option. Finally, possible future approaches are reviewed, including in vitro maturation of nonantral follicles, the artificial ovary, oogonial stem cells and drugs to prevent follicle loss.