Recent drastic advances of cryobiology and cryotechnology have enabled the cryopreservation of mammalian embryos and gametes. Improved vitrification methods have made it possible to preserve pre-fertilized oocytes with little loss of viability. Using a highly efficient vitrification method with ultra-rapid cooling (the Cryotop method), nearly 100% post-thaw survival rates have been obtained for human oocytes. These oocytes also have similar developmental ability in vitro after ICSI and IVC, and also to the term after ET. High post-thaw survival and pregnancy rates by the Cryotop method have been repeated at many IVF faculties throughout the world. The Cryotop method has contributed to the establishment of oocyte banks for unmarried cancer patients to preserve their fertility after chemo- and radio-therapy. Successful human oocyte banks have been established worldwide, resulting in the birth of more than 300 healthy babies so far.