"It's an incredible thing to put yourself through.
"It's a privilege to meet them and know them."
The research involves 18 people who have given a kidney without knowing who it will go to since this first became possible here in 1998.
They are known as "non-directed" donors.
Dr Cross said the practice in the South Island had begun as the result of one individual who was insistent that she wanted to give a kidney.
Kidney transplant programmes around the world had initially been reluctant to accept such donors as they assumed it was not something someone "in their right mind" would do.
It involved having "a reasonably large" operation, the removal of one half of a vital organ, the pain of recovery, and all for no gain.
Some centres still took the approach the donors must have an ulterior motive; that it was crazy risk-taking behaviour by people who must have some underlying wish for adulation or attention or "some maladjustment".
That first determined woman donor went through an "extremely long process", jumping through all the hoops put in front of her and convincing people through multiple assessments that she was of sound mind, Dr Cross said.
All three New Zealand centres where transplants are carried out - Christchurch, Wellington and Auckland - now accept kidneys from "non-directed" donors and detailed protocols have been developed.
Donors and recipients do not meet and information is kept anonymous to avoid unwanted attention from either party and reduce the possibility of anyone trying to gain from the procedure.
Communication between donor and recipient can be done through the transplant centre, but such communications will remain anonymous.
Donors are not paid.
They can receive some support through Work and Income, but often have to rely on an employer to allow them to take sick leave.
Dr Cross said Christchurch, which had done 19 transplants from such donors, had accepted such donations earlier than the others and had done the most.
The centre carries out 10 to 20 transplants annually and has done more than a hundred altogether.
The figures for non-directed donors were high compared with Australia where he understood only about eight such donors had given kidneys.
It was difficult to know why there was such altruism in New Zealand and in the South particularly.
It may have much to do with the smallness of the country.
The research involves interviews with the 18 surviving donors (the other one has died, not connected to the kidney donation).
The willingness of all 18 to be involved was "typical of these people", Dr Cross said.
This work has been carried out by Dr Allison Tong, the lead researcher for the project, and funded by Kidney Health Australia and Kidney Health New Zealand.
Dr Tong is a research fellow at the Centre for Kidney Research at the Children's Hospital, Westmead, Sydney.
It is hoped that the resulting paper will be of international interest.
Dr Cross, the project's principal investigator and author, said researchers wanted to find out how the donors felt looking back some years later.
Were they still happy they had done it, or did they experience a sense of loss?There would also be some exploration of the reasons people made the decision and finding out a bit more about "what makes these people tick".
It was already known the donors were an equal mix of men and women, from all walks of life, some with religious convictions, but not all.
Not all had known someone with kidney failure.
Dr Cross said matching of donations to recipients had not been a problem.
About 100 people in the South Island were waiting for transplants and about 500 throughout New Zealand.
Many people not prepared to be a live donor might consider donating their organs after death.
Often, people thought being listed as a donor on their driver's licence meant that if they died unexpectedly their organs were automatically donated.
Dr Cross said that was not the case, as family members could veto that at the time of the death.
• Accordingly, it was important people interested in donating their organs after death discussed the issue within their families and made their feelings clear.
There were benefits for the family in the long run, Dr Cross said.
"Most families look back , once they have got through the grief, and see it as the positive silver lining coming out of a terrible situation."
Anyone interested in being a live donor should contact the transplant co-ordinator at Christchurch Hospital, Sarah Armstrong, on (03) 364-1041 to discuss the possibility further.
Prospective donors must be over the age of 18 with two healthy kidneys and general good health.
Tests and assessments, including psychological evaluation, can take six to nine months.
