Oocyte cryopreservation entails important potential advantages for human IVF, offering a less ethically disputable alternative to embryo cryopreservation, simplifying and making safer oocyte donation, and giving an opportunity for fertility preservation to women at risk of premature ovarian failure as an effect of genetic factors or chemo- or radiotherapies. Oocyte cryopreservation could also meet the expectations of women wishing to preserve their fertility for social reasons. In the last few years, advances in cryopreservation methodologies have dramatically improved the efficiency of oocyte cryopreservation, leading to the birth of over a thousand babies and challenging the supremacy of embryo cryopreservation as the preferred form of fertility preservation. This text has been conceived with the aim of offering a comprehensive view of the state of the art of oocyte cryopreservation. It covers fundamental concepts of low temperature storage (controlled rate slow cooling and vitrification), aspects of oocyte physiology relevant to the process of cryopreservation, essential biological and clinical evidence, and ethical implications of oocyte cryopreservation, thereby providing a complete overview of progress in this strategy in assisted reproduction.