Background: it has been demonstrated in various experimental studies that radiation exposure produces a negative impact on the processes of spermatogenesis associated with the disturbances of the microcirculation processes in the testes and the development of cellular and intracellular disintegration expressed as destructive changes in the cells leading to their death. Aim. The objective of the present study was to detect the ultrastructural abnormalities in the cells of Sertoli and spermatogonia under conditions of their exposure to radiation and to identify the peculiarities of their regeneration under the influence of the therapeutic and prophylactic application of low-intensity ultra-high frequency (UHF) electromagnetic radiation (EMR) and low-intensity low-frequency magnetic field (MF). Material and methods. The experiments were carried out on 28 non-pedigree mature male rats with the body weight 180—220 g that were divided into four groups. The first study group was comprised of the animals exposed to radiation followed by the application of low-intensity ultra-high frequency UHF electromagnetic radiation EMR. The rats in the second study group experienced effects of radiation and low-intensity low-frequency MF. The animals of the third (control) group were exposed to radiation alone, and those comprising the fourth group 1 (only radiation exposure) were considered to be intact. Results. The studies with the use of electron microscopy showed that the therapeutic and prophylactic application of low-intensity ultra-high frequency (UHF) electromagnetic radiation and low-intensity low-frequency magnetic field caused the decrease in the number and the severity of post-radiation defects in the treated cells together with the increase of the number and size of mitochondria as well as hyperplasia of ribosomes; moreover, it promoted cellular and intracellular regeneration. UHF electromagnetic radiation had a more pronounced stimulating effect on the regeneration processes as compared with low-frequency MF. Particularly active processes of intracellular regeneration evolved in Sertoli cells; they were manifested as the increase in the number and size of mitochondria, enhanced hyperplasia of ribosomes, and formation of polysomes and new membranes of the granular endoplasmic reticulum. In spermatogonia, intracellular regeneration was less pronounced than in the Sertoli cells but was accompanied by enhanced cell regeneration and a greater number of reserve stem/progenitor cells. Conclusions. The results of the present study provide a rationale for the possibility of the application of a low-frequency magnetic field and especially UHF electromagnetic radiation for the further development of the promising therapeutic and preventive technologies with a view to their introduction into routine clinical practice dealing with radiation-induced pathology.