Major advances in techniques and the development of new immunosuppressive drugs and strategies have led to transplantation becoming the treatment of choice for end stage organ failure, with patients achieving long term survival and a high quality of life. The cost benefits of transplantation have been well recognised and renal transplantation alone saves huge amounts of money spent on dialysis.¹ Despite the many advantages of organ transplantation, this treatment is unavailable to many who would benefit, owing to the shortage of organs. The gap between the numbers on waiting lists and the available organs continues to widen as the number of donors declines in many countries.² The unmet need for organs may be still higher, as transplant physicians are selective about who they list because of the lack of donors, and the potential need for transplantation may exceed availability even if all suitable organs were used.

The shortage of human organs for transplantation has stimulated intense research into alternative sources. Consideration has been given to the use of old world monkeys and apes, but the need to rear the animals in isolation raises ethical concerns. In addition, viruses from non-human primates are perceived as a particular risk to humans. Pigs are currently the only animals being seriously considered as a source of organs for transplantation to humans. Pigs have been domesticated and have lived close to man for hundreds of years, grow quickly to a suitable size, produce large litters, can be reared in specific pathogen-free conditions, and there is already considerable expertise in pig husbandry. The ethical concerns are less, given that animals are reared for human consumption and porcine tissues are already used in prosthetic heart valves.

Xenotransplantation (the transplantation of tissues from one species to another) has several potential benefits provided the various obstacles can …