Attempts to freeze-dry spermatozoa are not new. Successful conception and full-term development using freeze-dried spermatozoa were reported in the cow and rabbit prior to 1960. However, these preliminary results have not been confirmed. Spermatozoa become defective in motility after freeze-drying and are unable to fertilize eggs both in vivo and in vitro. However, in 1998, freeze-drying of mammalian spermatozoa was demonstrated without loss of genetic or reproductive potential. Freeze-dried spermatozoa support normal development when injected directly into oocytes by means of an intracytoplasmic sperm injection (ICSI) technique. Recent investigations of freeze-dried sperm have focused on the factors affecting freeze-drying in spermatozoa in an effort to make it possible to store the male gamete at ambient temperature. The pressure level at primary dryied of freeze-drying spermatozoa, in addition to the components of the suspending solution, appears to be an important factor for long-term preservation of freeze-dried spermatozoa.