Cryopreservation of mouse spermatozoa has been widely applied for maintenance of genetically modified mouse strains. Although cryopreservation of spermatozoa is simpler, less time-consuming, and less costly than of embryos for maintaining transgenic or gene-disrupted mouse strains, maintenance of cryopreserved spermatozoa still has high running costs because of the need for a constant supply of liquid nitrogen. It has been reported that freeze-dried mouse spermatozoa are capable of participating in normal embryonic development after injection into oocytes, and so they have attracted a great deal of attention as storable gene resources. However, it is particularly essential to assure long-term preservation for several decades or centuries. The application of the determination of accelerated degradation kinetics calculated by extrapolation of Arrhenius plots to the preservation of freeze-dried mouse spermatozoa is a possible solution. This theory also is being applied to long-term stability of drugs. In this issue, we introduce recent studies of freeze-dried mouse spermatozoa.