Although somatic cloning efficiency of not more than 1? Animals born 2% relative to the number of reconstructed oocytes, the cloning is used to obtain transgenic animals producing milk or urine of human therapeutic proteins to rescue dying breeds and species of mammals, and even restitution of species already extinct. Work is underway aiming to achieve? by somatic cloning? organs for xenotransplantation as well as differentiated cells presenting cell therapy for the perspective of many diseases. Discussed emerging as a result of past experience doubts about the mechanisms underlying methodology of cloning (oocyte activation, the choice of the G0/G1 phase of the cell cycle nucleus) and causes developmental abnormalities in cloned animals and the age of cloned animals.