DIANE SAWYER (ABC NEWS)(OC): We are grateful to "The New York Times" for this story which took us inside a remarkable event, a kind of relay race of generosity. 90,000 people need kidney transplants tonight. 4,500 will die each year. But the man who founded the National Kidney Registry figured out that all of us would find it in our heart to help strangers if it in turn saved someone we knew and loved. Well tonight the biggest kidney donor marathon in history.
DIANE SAWYER: It's the incredible algebra of human kindness. One person deciding to save a life of a stranger whose family, in turn, saves the life of another stranger and on and on. All you need is the stranger who starts it.
RICK RUZZAMENTI (FIRST KIDNEY DONOR IN CHAIN): A stranger is just as important as a family or friend.
DIANE SAWYER (ABC NEWS)(VO): Enter Rick Ruzzamenti, an electrician, who said work was slow right now. He had time on his hands, enough time to give a gift.
RICK RUZZAMENTI: It's like there's some virtue to being kind and helpful to your family and friends but that's easy, you know, I mean if the world could love strangers and be as kind to them as to their family and friends, I mean the, you know, world problems would be solved.
DIANE SAWYER: Getting nothing in return, he decided to give his kidney to someone whose family couldn't provide a match. As a result, his kidney traveled all across the country to New Jersey to the family of a man who, in turn, donated one of their kidneys to Brooke Kitzman from Michigan. And as we said, it went on and on, an ex-girlfriend getting a kidney because her ex-boyfriend gave one to someone else, the old prom date from Queens, New York, Gregory, donating a kidney so Zenovia could get a kidney from Samantha in Porterville, California. The mastermind behind it all is an ex-marine with an MBA and his own company and a 10-year-old daughter who once had kidney failure. 15 people tried to donate until she got the match.
GARET HIL (FOUNDER AND CEO OF NATIONAL KIDNEY REGISTRY): When I, you know, saw these systems, I thought there needed to be a better way. And that's what drove us to create the National Kidney Registry.
DIANE SAWYER : It must have been a terrifying time.
GARET HIL: It was very stressful. Yes.
DIANE SAWYER : So you're giving back. You're paying forward.
GARET HIL: Yes. You might say that.
DIANE SAWYER: And so it was before dawn matching profiles logistics, blood types. Four months, 17 hospitals, 11 states, until this largest chain of generosity ever ended with the 30th transplant, 47-year-old Donald Terry.
DONALD TERRY: I felt myself was like dying on dialysis. When the doctor called me and told me that he had a kidney and that he was going to donate. I can't tell you how I actually burst down in tears.
DIANE SAWYER: And Terry had no idea that the two people watching over him was that ex-marine and the stranger who, on impulse, walked into the hospital.
RICK RUZZAMENTI: If you believe in God, you could say, well, maybe God gave us an extra kidney so that we could give away. You know, if I had another kidney, I would donate that one too.
DIANE SAWYER: So many people connected by what it really means to be human.
FEMALE (VIDEO): Thank you.
DIANE SAWYER: Many of them wanting to send a message like Paulette from Chicago, recipient number 12.
PAULETTE BEHAN: The words "thank you" really aren't enough but they're the only ones I know to say. So thank you.