About 150 commercial sperm banks exist in the United States; these banks are often clustered around universities where many intelligent and virile young men live.  The qualities present in college students are in high demand among infertile couples trying to have a baby.  Thus, approximately 50 to 90 percent of all sperm donors are college students!  The remaining 10 to 50 percent of donors come from all walks of life and have a variety of interests, values, and skills.

Only 5 percent of all male applicants who apply to be a sperm donor meet the criteria to donate sperm.  The following conditions immediately disqualify a potential donor from donating sperm:

• Men who have a history of certain diseases in the family (i.e. cystic fibrosis, sickle cell anemia, etc.) cannot donate sperm.
• Homosexual men and men who have had sex with other men cannot donate sperm.
• Intravenous drug users are automatically disqualified.
• Men who have visited areas where considerable numbers of AIDS cases have been reported and have had sex with either women or men living there are prohibited from donating.

Applicants go through a rigorous screening process before they are cleared to donate sperm.  Donor screening consists of questionnaires, blood screening, specimen screening, genetic analysis and a physical evaluation.  This process includes:

• Comprehensive interviews about sexual behavior, family background and reasons for participating in the sperm donation program.
• An extensive family history (spanning in some cases, three generations), is taken and evaluated.
• The semen is analyzed for sperm cell count, forward sperm cell motility, and normal sperm morphology.
• The candidate is tested for infectious diseases like HIV, Hepatitis B, and Hepatitis C (and others).
• ABO-Rh blood typing.
• Genetic testing for cystic fibrosis.

This screening process takes from 8 weeks to 6 months depending on the sperm bank to which the man is applying.  If the man is one of the lucky 5 percent of applicants who are accepted to donate, he will be paid from $40 to $100 for each semen sample.  A donator can sire a maximum of 10 children and potentially make up to $6,000 in a year.  Sperm donation is usually motivated by money rather than altruism.

The donation process is simple.  The man walks into a private room which is usually stocked with pornography and masturbates into a sterile container.  The semen sample is collected from the container and is mixed with a cryopreservative solution, divided in aliquots, sealed in vials and frozen with liquid nitrogen.  The frozen semen is stored at -321 degrees F.  When needed, the semen sample is thawed and used in artificial insemination.

Source: Stanford edu