Xenotransplantation is a concept, which was pioneered a century ago, when transplanting human organs was considered ethically controversial. It is the transplantation of living cells, tissues or organs from one species to another. The development of xenotransplantation is, in part, driven by the fact that the demand for human organs for clinical transplantation far exceeds the supply. Xenotransplantation raises concerns regarding the potential infection of recipients with both recognized and unrecognized infectious agents and the possible subsequent transmission to their close contacts and into the general human population.