Cryopreservation, in vitro maturation, fertilization and culture can be applied to various processes across a wide range of species, that is, for the breeding and reproduction of farm animals, preservation of genetic variants in laboratory animals, and the conservation of wild species. In particular, the storage of oocytes by cryopreservation and IVM following cryopreservation, might become effective alternative assisted reproduction treatments for infertile patients. For example, in a clinical context, these techniques might be important for patients who are at risk of losing their ovarian function because of extirpative therapy, chemotherapy or radiation. Thus, it is important for assisted reproductive technology to improve IVM and cryopreservation techniques. In the present review, we introduce our recent studies on vitrification and IVM of germinal vesicle stage oocytes in animals. (Reprod Med Biol 2007; 6: 61-68)