Marshall's name was added to a bone marrow registry, and he was told that he would be contacted if he ever came up as a match for someone in need of a bone marrow transplant, he said.
"I never thought in a million years I'd be picked," said Marshall, 37, of Boonsboro.
The call came five years later.
Marshall was notified in March that a match had been found for his bone marrow, he said.
After an extensive health screening over the phone, Marshall was asked to donate more blood for further testing. He then heard nothing for three months, he said.
In June, Marshall was contacted with news that his marrow was a perfect match for a 42-year-old woman dying of leukemia. He was told only that the recipient lived in another country.
Marshall was then assigned an independent physician whose "job was to eliminate me - to find something wrong with me so I couldn't go through with this," he said.
The physician evaluated more of Marshall's blood, his family medical history and the results of a complete physical. The information was then sent to the recipient's doctors overseas, Marshall said.
He was approved as a donor on Aug. 5. Surgery was scheduled for Aug. 27.
Marshall knew he could change his mind at any time, but he also knew doing so could mean death to the waiting recipient, he said.
Bone marrow transplant patients often undergo chemotherapy and/or radiation to destroy diseased cells in the body prior to the transplant. This procedure also destroys the stem cells in the marrow, leaving patients extremely susceptible to infection until well after the transplant, according to the National Bone Marrow Transplant Link Web site.
Marshall knew his bone marrow recipient had already begun chemotherapy, he said.
"If I would have backed out, she would have died," he said.
Doctors at The Johns Hopkins Hospital in Baltimore extracted bone marrow from Marshall's pelvis during a one-hour procedure - from which Marshall spent nearly seven hours recovering - on Aug. 27, he said.
A courier waiting outside the operating room then transported the marrow to Baltimore-Washington International Airport for immediate delivery to the recipient, Marshall said.
He sent a card along with his bone marrow, he said.
Marshall - who returned to work the day after his surgery - hopes to receive a progress report regarding the woman's condition within the next six months. In 2004, he may have the opportunity to learn the woman's identity, he said.
"I would love to go see her or have her come see me, but that's up to her," Marshall said.
He has been removed from the bone marrow transplant registry for the next year but could be asked to donate more marrow for the same recipient at any time, he said.
"That would be a tough one," Marshall said, "but if that's what it'll take to save her, I'd do it."