[en] At present many countries actively develop the nuclear technologies of energy production. Simultaneously, a tendency persists for the propagation of nuclear weapons. Accordingly, the waste of the nuclear energy production and nuclear weapon industry products to be utilized constantly grow in amount. Besides, there is a risk of plunder of nuclear materials and diversions at nuclear plants. Therefore, in spite of the efforts that are constantly made to enhance the control and safety in this regard, there is still danger of radiation accidents and risk of environment contamination fraught with serious consequences for the biosphere. Today the radiation-ecological situation in the Caucasus-Caspian region may be considered favorable but the risk of its deterioration, as in the whole world, still persists. It should be taken into account that in this region two nuclear power complex plants, uranium mines and treatment facilities, research nuclear reactors as well as burial-grounds for radioactive waste are situated. Earlier (in the 70's-80's of the past century) 29 subsurface nuclear explosions (for geological survey) were performed in the northern part of the region. Release of radionuclides to the environment results in increased ionizing radiation background, which, in combination with other technogenic agents may be a serious hazard to all living things and produce a variety of harmful effects in living organisms, depending on the dose. The genetic consequences of radionuclide contamination of environment and of the combined effect of low-intensity radiation and non-radiation factors on humans (as well as on other living things) have been the subject matter of numerous recent scientific discussions. Studies in this field are essential for assessing the hazards associated with increased ionizing radiation background under the conditions of contamination of environment by anthropogenic agents as well as for development of techniques and means for radiation safety and prophylaxis of human disorders. Thus, it was found that the action of low-dose ionizing radiation on living organisms might induce an adaptive repair response in them aimed at decreasing the genetic consequences of the exposure. However, the potentialities of defense and repair systems of an organism are limited, so an increase in genome lesions may cause inheritable mutations, cancer and other pathologies, and death. DNA lesions caused by ionizing radiation in small and sublethal doses can essentially be repaired, whereas unrepaired lesions and errors of repair, replication, and recombination systems lead to formation of mutational changes in DNA sequences. These changes may be transmitted to daughter cells and induce genome instability in the progeny. Induced genome instability in survived somatic cells is characterized by persistence of a high level of acquired variability in many generations of these cells. Genome instability manifests itself as an increased frequency of karyotypic anomalies, chromosome and gene mutations, clonal heterogeneity, and malignant transformation in the progeny of cells exposed to DNA-damaging agents. Besides, cells with genome instability show increased amplification of genes and changes in their expression, as well as disturbances in their differentiation, delays in reproductive death and other phenotypic characters of abnormal development. Whereas some progress has been made towards knowledge of genome instability in the somatic cells of mammals, the radiation-induced genome instability in germ cells transmitted to individuals of the next generation is still not clearly understood. At the same time, evidence has been obtained which suggests that the transmission of genome instability to the somatic cells of the progeny from the germ cells of gamma - radiation-exposed parents is possible. This conclusion is based on the data on mutation frequency in the progeny of parents exposed to DNA-damaging agents. For instance, a significant increase in mutation frequency, as determined from analysis of polymorphism of protein markers, has been observed in children of parents survived from A-bomb attacks in Hiroshima and Nagasaki. An increase in cancer rate has been registered in children of parents exposed to ionizing radiation or employed at nuclear technology facilities under the conditions of increased radiation background. In rodents, the progeny born to radiation-exposed male parents showed increased gene and chromosome mutations and tumor induction. However, the best-reproduced results on genome instability transmission from parental germ cells to the somatic cells of the progeny were demonstrated by changes in variability of micro- and macro satellite tandem repeats of DNA. Thus, experimental and epidemiological evidence has been obtained that radiation-induced changes formed in the genome of survived germ cells lead to increased genome instability in the somatic cells of the progeny in animals and humans. This inheritable genome instability may cause a decrease in the quality of human health