BACKGROUND. The relevance of the work is due to the importance of the problem of regeneration of organ tissues (myocardium, liver and brain) for fundamental science and practical medicine. The purpose of the work is to summarize many years of personal experience in studying the regeneration of pathologically altered vital organs in mammalian fetuses in the natural conditions of a living organism. Material and research methods. Rabbit fetuses were subjected to mechanical injury to the heart and brain, and rat fetuses were subjected to similar liver damage. The work was carried out with a number of classical and modern methods (histological, morphometric, electron microscopic and immunohistochemical). Research results. As a result of healing of mechanical trauma in the heart of rabbit fetuses, a complete restoration of the dead area was obtained. In the liver of fetal rats, the organ was not completely restored, there was only a decrease in the area of fibrosis that arose at the site of the dead tissue, compared with the control. The difference in the outcomes of the healing of injury to the heart and liver, the authors explain by the absence of an exudative reaction to injury in the heart of rabbit fetuses, while in rat fetuses this reaction took place at the time of injury. Conclusion. The results obtained give reason to believe that the vital organs of mammalian fetuses have high regenerative potencies.