Couples who cross-donate kidneys.

But UNOS is slow and clunky, and people are dying while they wait for a national swap program. Enter the Paired Donation Kidney Consortium, which aims to link 30 transplant programs in nine states. The group, which began in Ohio, has registered 71 recipients and done 10 transplants in 19 months, with six more scheduled.

As more hospitals join up, the consortium's backers imagine that as many as 2,500 donors and recipients could be registered annually, yielding at least a quarter that number of transplants. The challenge, doctors say, is to get patients to realize that anyone can be a donor. So, if you have a loved one with kidney failure, get ready for the following phone call: "Remember when you offered me your kidney, but you couldn't donate because we weren't a match? Well—did you really mean it?"