By Nima Sarvestani
Director, Kidneys for Sale
On streets and in town squares in Iran, young men and women can be seen holding signs offering their kidneys for sale.
The buying and selling of kidneys in Iran is regulated by the state
One of them reads: "Immediate offer! Kidney for sale, young man, 22, healthy, blood type O positive. Tel 09122... "
Every year, 1,400 Iranians sell one of their kidneys to a stranger.
At the Tehran branch of the Association of Kidney Patients, one of many agencies set up to facilitate the trade, the reception is full of people.
In the narrow, drab corridors, people are waiting in line, either to fill in forms, answer questions, undergo tests or be X-rayed, and finally to be operated on.
Activity is intense, bordering on the chaotic.
Registers are filled in, photographs of patients are pasted onto small cards, and the telephone rings endlessly.
Prices are inquired about and haggled over.
Some people get upset at what they see as low prices and leave in anger.
One man wishes to sell because his child has been burned in a fire and he needs the cash for an urgent operation.
Another wants to know why he has not received the $1,250 (£650) he is due from the state.
A third shouts: "They want it practically for free. They think I'm selling meat."
Their desperation is obvious.
Mehrdad is 23 years old and in deep financial trouble.
Two years ago he was working in the construction industry, had a stable income and was planning to get married.
There are 137 agencies around Iran and 23 transplant clinics
But just after his wedding he lost his job and his attempts to find a new one were fruitless.
The debts from his wedding were still unpaid and the pile of unpaid rent bills kept growing.
Desperate, he decided he would sell a kidney, hoping to receive around $7,500 (£4,000) for it.
At the clinic Mehrdad was told that the number of sellers had increased so drastically over the past year that prices had plummeted, and unfortunately for him he is blood type A, one of the most common... driving the price even lower.
He was told the most he could expect was $3,700 (£2,000).
When Mehrdad returned to the clinic for his final batch of tests, he was told they had found a match for his kidney.
Mehrdad decided to give his kidney to Shiva on trust and accept payment after
Twenty-two year-old Shiva had already gone through one transplant operation but her body had rejected it and it had stopped functioning after two years.
Her father was still paying the debt from the first transplant.
After much haggling Mehrdad and Shiva settled on a fee.
The state was to pay Mehrdad $1,250 (£650) and Shiva's family had agreed to pay him another $3,000 (£1,600).
It was less than he had hoped, but enough to help him clear his debts.
Normally the donor receives half of the money before the transplant takes place but Shiva's father kept playing for time and tried to delay the operation.
It seemed he was having trouble coming up with the cash.
Shiva (l) and Mehrdad (r) became friends during their ordeal
Although Mehrdad became frustrated and impatient to pay his debts, he and Shiva spent a lot of time together at the clinic and a strong friendship blossomed between them.
Mehrdad decided to give his kidney to Shiva on trust and accept payment after the transplant.
He was nervous about the operation. "The other night I dreamt I was on the operating table. They cut open my stomach and said: 'Look! He has no kidneys!"
Two months on from the transplant, both Mehrdad and Shiva had made a full recovery, but Mehrdad's financial problems are far from over.
The money helped to pay off his debts and he even managed to buy a car to start a new career as a taxi driver, but he was involved in an accident and the car was written off.
Unemployed once more, Mehrdad reflects on everything that has happened to him.
He opens a letter Shiva gave to him on their last day in hospital, in which she refers to him as her "rescuing angel" and continues: "I hope that I will care for your gift in a good way throughout my life and feel that you are with me all the time."
This World: Kidneys For Sale was broadcast on Tuesday, 31 October, 2006 at 2150 GMT on BBC Two.