George Wesley Santos, MD, 1928–2001 On January 21, 2001, the transplantation community lost one of its visionaries, Dr. George Wesley Santos. Among his many friends and colleagues around the world, he will be remembered not only for accomplishments that moved the field of bone marrow transplantation (BMT) from its infancy to where it is today but also for his generosity and his friendship. George developed his interest in BMT while serving in the Naval Reserves at the U.S. Naval Radiologic Defense Laboratory in San Francisco from 1956 through 1958. He and his colleagues were asked to study the effects of high-dose radiation on animals and to determine whether BMT could rescue lethally irradiated animals. George was one of the first to realize that the “wasting” or “secondary” disease after allogeneic BMT in animals represented, in fact, a graft-host reaction. Although the military's concern was focused on the aftermath of a nuclear disaster, George saw the additional potential of this approach as a treatment for cancer and life-threatening hematologic disorders. It was during this time that George also cultivated his commitment to integrating basic laboratory research with the clinic, what George liked to call “engineering” (no doubt a tribute to his undergraduate alma mater, Massachusetts Institute of Technology, where he also earned a masters in biophysics) but now better known as translational research. Following his military service, George returned to Johns Hopkins, his medical school, for residency training. In 1960, he became Albert Owens's first fellow in what would be called more than a decade later the subspecialty of oncology. George and Al soon began their ground-breaking studies into the effects of high-dose cyclophosphamide on the immune system and transplantation tolerance in animals. These studies rapidly led to the first clinical trials of high-dose cyclophosphamide as pretransplant conditioning. The site of these studies was the Johns Hopkins Oncology Unit, initially housed at the old Baltimore City Hospital. There George founded the Hopkins BMT Program in 1968, the same year he transplanted his first patient. With his colleagues in the early days, George engineered much of what is now standard of care in BMT. Examples include high-dose cyclophosphamide and later busulfan (as an alternative to total body irradiation) for pretransplant conditioning, cyclosporine for graft vs-host disease, 4-hydroperoxycyclophosphamide (4HC) for autograft purging, acyclovir as prophylaxis for herpes infections, and counterflow centrifugal elutriation for T-cell depletion of allografts. George's contributions go well beyond science. He was a tremendous role model for those who were fortunate enough to work with him, and he was a compassionate and caring physician. Although George received many prestigious awards, it was rare to hear George talk about his accomplishments. Rather, it was common for him to brag about the achievements of his patients by name, and his office contained a wall of photographs of the patients he had treated. He loved to recount the wedding of one of his patients who was transplanted 15 years earlier. He always credited the nursing and support staff, who were integral to the success of his program. He was hard-working and focused (some would say driven), yet he was one of the most forthrightly honest individuals I have known. He could be demanding and his probing questions are legend (few ever forget giving a lecture when George was in the audience). George loved a healthy discussion (argument) for the purposes of provoking thought and stimulating new ideas. Despite strong and passionate convictions, he could always be persuaded by strong data. A whole generation of Hopkins-trained translational scientists look to George as their intellectual and spiritual mentor. The world of biomedical science has recently embraced the concept of translational research, or engineering, to use George's term. George, however, was showing the Hopkins medical community how to engineer decades before it was in vogue. Moreover, his animal studies into transplantation biology continue to guide many of our current “new” therapeutic approaches, including non-myeloablative transplants and the use of high-dose cyclophosphamide for autoimmunity. We miss you, George. All of your patients, colleagues, students, and friends thank you for your accomplishments, vision, and support.