China has denied a BBC report that organs taken from executed prisoners are sold for transplant.
China executed at least 1,770 people in 2005
Foreign ministry spokesman Qin Gang said such organs could be transplanted but the use was "very cautious".
Mr Qin said: "The sales of organs are prohibited, [donating organs] must have the consent of the donor himself."
The undercover BBC report said one hospital confirmed it could provide a liver for £50,000 ($94,400), and it could come from an executed prisoner.
AFP news agency quoted Mr Qin as telling reporters that death-row prisoners had to provide written consent.
The donation must also be approved by provincial health officials and the provincial high court, he said.
"Concerned health administrative departments deal with those operations in strict accordance with the law," Mr Qin said.
'Present to society'
The undercover investigation by the BBC's Rupert Wingfield-Hayes said that organs from death row inmates were being sold to foreigners who needed transplants.
He visited No 1 Central Hospital in Tianjin, ostensibly seeking a liver for his sick father.
Officials there told him that a matching liver could be available in three weeks.
One official said that the prisoners volunteered to give their organs as a "present to society".
He said there was currently an organ surplus because of an increase in executions ahead of the 1 October National Day.
China executes more prisoners than any other country in the world. In 2005, at least 1,770 people were executed, although true figures were believed to be much higher, a report by human rights group Amnesty International said.
In April 2006, top British transplant surgeons condemned the death-row transplant practice as unacceptable and a breach of human rights.
But the No 1 Central Hospital carried out 600 liver transplants last year, our correspondent says, and the organ transplant industry has become big business.