Oocyte cryopreservation entails important potential advantages for humanIVF, offering a less ethically disputable alternative to embryo cryopreservation,simplifying and making safer oocyte donation, and giving an opportunity forfertility preservation to women at risk of premature ovarian failure as an effectof genetic factors or chemo- or radiotherapies. Oocyte cryopreservation couldalso meet the expectations of women wishing to preserve their fertility forsocial reasons. In the last few years, advances in cryopreservationmethodologies have dramatically improved the efficiency of oocytecryopreservation, leading to the birth of over a thousand babies andchallenging the supremacy of embryo cryopreservation as the preferredform 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 andvitrification), aspects of oocyte physiology relevant to the process ofcryopreservation, essential biological and clinical evidence, and ethicalimplications of oocyte cryopreservation, thereby providing a completeoverview of progress in this strategy in assisted reproduction.