The American Bone Marrow Donor Registry, based in Worcester, Mass., and the National Marrow Donor Program in Minneapolis, Minn., keep computer files on about 4.4 million people worldwide who have volunteered as donors. The odds of finding a matching donor average about 1 in 20,000--better for whites, tougher for others. An estimated 30,000 bone-marrow transplants are performed each year worldwide. But it is estimated that 60,000 others needing transplants die without ever finding a donor.

Majewski and her husband first volunteered as donors 10 years ago, when a friend asked them to help a family member with leukemia. They underwent initial blood tests, known as hla typing, for a series of four genetically determined traits that, along with two more traits tested at a second level, must closely match those of the patient for a transplant to be accepted by the body. Neither Teri Majewski nor her husband matched, but they let the American Bone Marrow Donor Registry keep their records.

Ten years passed, and then the Majewskis got a call saying Teri was a match for a desperately ill patient overseas. Teri had been hoping to become pregnant again, but expectant mothers cannot donate bone marrow. She decided to postpone the pregnancy in order to help, even though it would be months before the patient would be ready for the transplant. Majewski insists it was not hard to make up her mind. "There's no choice," she says. "You're talking about saving somebody's life. There is no decision."

Similarly, Majewski will not acknowledge that hers is a heroic act; it is simply the right thing to do. She says she is not scared. Her suffering will be nothing compared with that of the patient, she insists. "And I'll regenerate the marrow without a problem." If bone-marrow cells could transmit their owner's grit and determination, the person who gets Majewski's would have it made.

Hans Klingemann, the physician who directs the bone-marrow transplant center at Rush, is to perform Majewski's harvest, along with Sharon Manson, a clinical nurse specialist. Each has done the procedure hundreds of times. Still, Klingemann is always worried about the donors. Although the risks of allergic reaction or stroke (if a patient has general anesthesia, instead of the spinal Majewski had) and dangers of infection are very small, they are nonetheless real. People who have surgery take such risks, but they usually gain some benefit that makes the risks worthwhile. Bone-marrow donors like Majewski have nothing to gain, except perhaps a measure of grace.