1. We have developed a method for plotting C-curves of isothermal martensite transformation by analyzing the temperature and amplitude dependences of IF with thermostatic control in the range of temperatures of martensite transformation. We have obtained data on the inelasticity and microplasticity of the studied alloys in the course of isothermal martensite transformation and have determined the inelastic effects (internal-friction peaks) in warming the alloys up after the martensite transformation. 2. We have determined the activation energy of isothermal martensite transformation in an Fe−Cr−Ni−Mo steel within the framework of the theory of absolute reaction rates, namely,H≅20 kJ/mole. In alloys of the system Fe−Ni−Mo with a double kinetics of martensite transformation the activation energy changes fromH≅6–8 kJ/mole at the nose of the C-curve toH≅2–3 kJ/mole at a temperature approaching the point of adiathermal martensite transformation. 3. We have established the effect of the content of interstitial atoms on the kinetics of the change in the properties of the alloys in subsequent cooling in the temperature range of martensite transformation and the role of trapping of dislocations by interstitial atoms. The formation of saturated impurity atmospheres on dislocations diminishes the role of the dislocations as sites of martensite nucleation due to compensation of the energy of elastic distortions around the dislocations and growth of the energy of formation of martensite nuclei, diminishes the mobility of the dislocations, increases the relaxation stability of austenite, and hampers the development of the isothermal kinetics of initiation and progress of MT.