The birth of the first nuclear transfer-derived cloned piglet resulted from the transfer of a nucleus from a 4-cell stage embryo to an enucleated oocyte. Although biotechnological procedures in swine have recently undergone tremendous progress, the efficiency of pig somatic cloning is still lower than in other species of farm animals and, when expressed as a proportion of reconstructed oocytes, it does not exceed an average of 5 to 10% blastocysts and 1.5% born piglets. The basic prerequisite

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... r practical application of this method is to improve efficiency. This requires further detailed studies. Development of pig somatic cell cloning was inspired not only by the necessity for quick improvement of the efficiency of the nuclear transfer technique in this species, but above all by its possible practical application for multiplication of transgenic piglets, for use in transplantation medicine and immunology, also pharmacy and animal breeding. A deficit of organs for human allotransplantation became a stimulus to the search for new, alternative sources of grafts. Therefore, a particularly attractive aspect of pig somatic cloning is the possibility of generating large numbers of transgenic pig organs for xenotransplantation. Compatibility with the human ones in size, anatomy, and physiology makes this an attractive proposition.