The Declaration of Istanbul, consistent with Resolutions 44.25 and 63.22 of the World Health Assembly, strongly condemns the sale of human organs. Principle 5 of the World Health Organization's Guiding Principles on Human Cell, Tissue and Organ Transplantation states:
"Cells, tissues and organs should only be donated freely, without any monetary payment or other reward of monetary value. Purchasing, or offering to purchase, cells, tissues or organs for transplantation, or their sale by living persons or by the next of kin for deceased persons, should be banned.
The prohibition on sale or purchase of cells, tissues and organs does not preclude reimbursing reasonable and verifiable expenses incurred by the donor, including loss of income, or paying the costs of recovering, processing, preserving and supplying human cells, tissues or organs for transplantation."
Commentary in the Guiding Principles justifies this prohibition as follows:
"Payment for cells, tissues and organs is likely to take unfair advantage of the poorest and most vulnerable groups, undermines altruistic donation, and leads to profiteering and human trafficking. Such payment conveys the idea that some persons lack dignity, that they are mere objects to be used by others."
In this section you'll find links to a number of articles discussing the issue of markets in human organs.