Salvatore Leto cringes -- visibly -- if you call his workplace a sperm bank. He prefers "male fertility evaluation center." The small freezer stocked with thousands of frozen semen specimens is just one facet of the Washington Fertility Study Center.

"Most of our work involves the husband of couples having fertility problems," says Leto, lab director of the center which looks like a posh doctor's office. It is one of about 15 frozen sperm banks around the country.

Leto first runs a series of tests on the man to determine if a malfunction on his part is inhibiting the couple's ability to conceive.

Roughly 10 to 20 percent of men tested still remain sterile after all treatment options are exhausted. Of these, about 40 percent of couples choose to have the woman impregnated by artificial insemination with donor semen -- what some people call a "hemi-adoption."

The fertility center can provide semen to the referring gynecologist. (Recipients can request a donor to match physical characteristics of the husband.)

Most of the donors are area medical students who are examined and screened for genetic disorders. Accepted donors are paid $20 per sample and may contribute semen for a maximum of five pregnancies. Donor records are coded to insure strict confidentiality.

In some cases where the husband has viable sperm, his semen is mixed with the donor sperm. Since "it only takes one sperm to fertilize an egg," this practice, points out Leto, allows the possibility of the husband being the father.

Human sperm banking boomed in the late '60s as a result of the demand for vasectomies, says Leto.

Entrepreneurs hoped men would buy "fertility insurance" by having their semen stored before the sterilizing operation, in case they decided to become fathers later. Some people even dreamed of large sperm-banking chains.

During this time Leto worked at a Baltimore sperm bank where, in 1972, it cost a man $80 plus an $18-a-year storage fee to have three specimens of his semen tested and frozen (at 321 degrees below zero) for as long as he liked. He, along with a licensed physician, could withdraw the semen for $30 and have his wife inseminated.

The response, however, was slim, says Leto, noting that in the last seven years only about three dozen men have requested such storage.

Insemination with frozen semen accounts for about 5,000 birth worldwide, according to J. K. Sherman, a professor at the University of Arkansas and chairman of the reproductive council of the American Association of Tissue Banks.

Births have been recorded using semen frozen for more than five years, according to Sherman, and women who have been inseminated with donor semen have returned to have a second child, using the frozen semen of the same donor.

Convenience, says Sherman, is a major advantage of frozen semen. It is available when needed and a woman can be inseminated several times, around her ovulation period, from the same donor. Frozen semen also can be screened for microbial contamination not detectable in fresh semen, and can be invaluable in small communities without access to donors.

Only an estimated 10 percent of artificial inseminations, however, are done with frozen semen. "It is slow in evolving partly because the population is not convinced it's safe," says Sherman.

Some doctors still question the use of frozen semen and say it should be used only by experienced practitioners at well-equipped research centers. Another deterrent is the high cost of installing equipment in private offices.

"Data prove it's safe," argues Sherman. "Now that more and more physicians realize this and with abortion laws as a further stimulus (limiting the number of babies available for adoption), there will be a further increase in the use of frozen semen."

Meanwhile, some men now are having their sperm frozen before undergoing chemotherapy, in case the therapy should leave them sterile. Sherman also predicts the use of "pre-environmental storage" for individuals who fear sterility from working with potential contaminants.