The microwave absorptivity of refractory metallic compounds at 2. 45 and 9.53 GHz is studied. It is ascertained that electromagnetic absorption is influenced by the grain size of absorbing particles: when it increases by 10 times, the absorptivity of ZrC, ZrSi 2 , HƒC, TaN, HƒN, ZrN, and NbC particles becomes higher by a factor of 7 and that of SiC, NbSi 2 , WC, B 4 C, MoSi 2 , and VN particles only by a factor of 2 to 4. It is connected with the physical properties of each compound: magnetic permeability (sign and magnitude), thermal e.m.f. (sign and magnitude), and active ac resistance. It is shown that stoichiometric impurity (namely, the formation of nonmetal vacancies) increases the microwave absorptivity, while the formation of substitution phases does not change the nature of microwave interaction. It is established that the morphology of particles with the same sizes does not influence the microwave absorptivity. It is proved that the measurement of absorption in weak fields can be used for nondestructive examination of refractory metallic compounds.