Semen cryopreservation is a procedure to preserve sperm cells. Semen can be used successfully indefinitely after cryopreservation. For human sperm, the longest reported successful storage is 21 years. It can be used for sperm donation where the recipient wants the treatment in a different time or place, or for men undergoing a vasectomy to still have the option to have children.
Semen is frozen using a newer flash-freezing process known as vitrification. Vitrification gives superior post-thaw motility and cryosurvival.
Thawing at 40°C seems to result in optimal sperm motility. On the other hand, the exact thawing temperature seems to have only minor effect on sperm viability, acrosomal status, ATP content, and DNA.