A light modification on the mouse embryos CARD simple vitrification protocol makes it possible the oocyte freezing. This rapid and handy method for cryopreservation of mouse oocytes has many advantages and multiple applications like banking the female gamete for future use, controlling the IVF timing, and facilitating the transgenic production. In this chapter we described the protocol for cryopreserving oocytes by simple vitrification method and the in-vitro fertilization carried out using fresh or frozen sperm. With this method, nearly all of the cryopreserved oocytes were recovered, resulting in more than 90% morphologically normal. From those oocytes used for in vitro fertilization, 89% of the oocytes were fertilized.