Xenotransplantation, the transplantation of organs, tissues and cells from animals, preferably pig-to-man, might be considered to become the transplantation of the future. Organs from domestic animals are available in unlimited numbers for xenogeneic transplantation and could swiftly solve the problem of organ shortages. Domestic animals of about the same size as human beings would be ideal organ sources. By selective breeding the anatomical and some physiological characteristics of these animals could be at least partly adapted to match the human body. However, the immunological mechanisms and the antigenicity of cells and their surface structures will remain obstinately unaltered. The only hope is that wide-reaching transgenic manipulation of animals, will soon achieve great changes in immunological and physiological circumstances.