Organ-transplant surgery is a proven approach to treating kidney failure, heart disease and other chronic illnesses. But most medically advanced countries are saddled with a wide gap between the number of transplant candidates and the number of available organs. Nearly 81,000 people in the U.S. are currently waiting for vital organs. Meanwhile, more than 6,000 Americans die every year because they don't get the organs they need in time. Some experts say allowing financial incentives for organ donation would eliminate the shortage. Others say the solution is xenotransplantation, or transplanting animal organs into humans. Meanwhile, critics contend the organ-allocation system favors affluent whites over minorities, and a global black market in organ parts targets desperately poor living donors.

Brian Hansen, a freelance writer in Boulder, Colo., specializes in educational and environmental issues. He previously was a staff writer for The Researcher and a reporter for the Colorado Daily in Boulder and Environment News Service in Washington. His awards include the Scripps Howard Foundation award for public service reporting and the Education Writers Association award for investigative reporting. He holds a B.A. in political science and an M.A. in education from the University of Colorado.