From Encyclopedia of Sex and Sexuality
For approximately forty years it has been known that human sperm can be frozen at very low temperatures (minus 196 degrees Celsius) and stored indefinitely. Facilities in which sperm are stored are known as “sperm banks.”
Sperm can be stored for two reasons. The first is to be used by the man producing the sperm himself, as, for instance, someone who is facing potential chemotherapy for cancer, surgical loss of one or both testicles, or someone who is contemplating a vasectomy but wants to preserve the potential for creating a pregnancy in the future. In these situations, a man can make arrangements with a sperm bank for storage of his own sperm. Sperm samples are collected and are frozen in liquid nitrogen; they can be stored indefinitely until their use is desired to establish a pregnancy. Generally, the man storing the sperm does not need to undergo special testing.
The second, and more common use of sperm banks is for the storage of anonymously donated sperm. A major cause of infertility in couples is the male partner’s low sperm count or low sperm motility (mobility). Although many of these men are helped with current medical and surgical treatments, there are many others for whom these treatments are unsuccessful or who are completely lacking in the ability to produce sperm. In general, anonymously donated sperm is used in these cases. The physical characteristics of the donor are matched by the physician to the physical characteristics of the man so that the resulting child will resemble his or her parents as much as possible.
Since it is possible to transmit sexually transmitted diseases(including AIDS) through donated sperm, donors are carefully selected and screened, and semen samples are checked for the presence of diseases. At present, all semen used for anonymous donor insemination in this country is frozen and quarantined for a least six months before use. After the quarantine period, but before the sperm is released for insemination, the donor is called back and retested for sexually transmitted diseases, specifically AIDS, before the sample is released.
Donors are typically college students, medical students, or young professionals, who are paid for several sperm samples that will be used for artificial insemination to produce pregnancies in women unknown to them.