Undeterred, Starzl retreated to the laboratory and, during the next two decades, perfected many of the surgical techniques that would make the mechanics of organ transplantation more routine. He refined a bypass system that allowed blood to be diverted to the lower half of the body during surgery: his patients no longer bled to death. He developed preservative solutions that extended the time that a liver could survive outside the body to 10 hours from 4 hours, making it possible to move organs between cities. But the defining challenge, as ever, was in immunology. Somehow it was necessary to suppress T-cells without jeopardizing the body's other defenses, without, as it would later become clear, inducing a condition like AIDS.

The first transplant patients were subjected to full-body irradiation, which destroyed their immunities altogether. Azathioprine, a powerful anti-cancer drug, was also used, but it proved ineffective over the long term. (Since the threat of rejection remains constant, transplant patients must take immunosuppressants as long as they live.) Periodically new strategies would evolve, but in each case the treatment turned out to be of no more than limited use. By 1980, the year before Starzl arrived in Pittsburgh from the University of Colorado, survival rates in transplant patients were poor, and even Starzl had concluded that without a more specific drug the procedure was likely to fade out of existence.

Cyclosporine more than revived the field. Also discovered underfoot, in a fungus from Norway, it was the first immunosuppressant to inhibit primarily T-cells: the body's other defenses were not seriously eroded. Early trials of the drug, however, revealed a terrifying medley of complications: diabetes, gout, neurotoxicity, tumors, mood swings. The worst of these, from a clinical standpoint, was kidney poisoning. Up to 80 percent of those taking the drug eventually developed nephrotoxicity that in many cases required further transplants. So toxic was the drug considered in early trials that it appeared to be lost. It was only when Starzl demonstrated that supplementing the drug with steroids allowed it to be given at acceptably lower doses did it become standard treatment. Suddenly, survival rates began to soar and transplantation took its place in accepted medical practice.

By the late 1980's, a similar rescue effort was needed with FK-506. Dr. Roy Y. Calne, the famed British transplanter, had given the drug to dogs and concluded that it severely weakened their arteries, killing the animals. Other tests in baboons were equally discouraging.

Starzl responded by mounting a full-blown research and development effort at the Pittsburgh Medical Center. Normally such efforts are conducted and underwritten by drug companies. But Starzl, determined to remain independent, refused Fujisawa's assistance. He forsook any financial stake in FK-506, instead asking for - and receiving - exclusive control over the drug's testing. The medical center has supported its star researcher with up to $8 million annually.

Though Starzl had wide experience with other immunosuppressant compounds like cyclosporine, he'd never directed the sort of basic research now required. And his new role was suited to his characteristic hubris - a surgeon in charge of providing the mountain of impartial data needed to prove the safety and efficacy of the drug that only he had access to.

Starzl quickly organized a team that performed hundreds of additional studies in mice, rats, pigs and baboons, eventually showing that Calne's dog studies were at least ambiguous and should not stop the drug's progress. Working closely with the F.D.A. and Fujisawa, Starzl's group produced evidence compelling enough to warrant testing FK-506 in humans. ''We were a human machine designed to get the drug through, to get it into clinic,'' recalls Dr. Michael A. Nalesnik, a pathologist pressed into service to measure dosages for Starzl.