[en] A state-of-the-art review is given of the properties of primary structure defects (Frenkel pairs) in silicon and geramanium. The process of formation of Frenkel pairs under conditions of irradiation with electrons or with γrays of ∼1 MeV energy at temperatures 4.2-300 K is considered. Approximate calculations are made of the energy of the interaction of the Frenkel pair components, vacancies (V) and interstitial atoms (I), in the approximation of an anisotropic elastic continuum subject to the electrostatic and elastic interactions. It is shown that the contribution of the flexoelectric effect may be considerable and should be allowed for in estimating the energy of the electrostatic interaction between V and I in those cases when one or both Frenkel pair components are electrically neutral. The mobility of V and I is considered, including the mobility during irradiation, and the energy spectra of vacancies and interstitials are discussed. The dependence of the probability of annihilation of homogeneous V and I on a whole range of parameters (temperature and intensity of irradiation, impurity composition of the irradiated material, densities of equilibrium and nonequilibrium carriers) is considered. An analysis of this dependence makes it possible to interpret qualitatively a complex nonmonotonic dependence of the efficiency of formation of primary and secondary (including impurity atoms) defects on the irradiation temperature and the radiation intensity and on the type of conduction of germanium. A nomogram is plotted for describing the dependence of the efficiency of defect formation in n-type germanium at 300 K on the radiation intensity and on the concentration of group V donors. It is shown that metastable Frenkel pairs are not observed in silicon, whereas germanium represents a unique opportunity for detecting such metastable pairs in an elemental semiconductor with the covalent type of binding. 68 refs., 7 figs., 2 tabs