1. The kinetics of the sintering of niobium carbide is largely determined by the presence in the latter of iron, which is picked up during milling in units with steel balls. Activated sintering was found to be exhibited by powder containing, in the starting condition, as little as 0.3 wt.% of iron. No upper limit of the activating action of iron has been established. 2. The activation of the shrinkage of specimens containing iron is induced by the formation of a liquid phase, which intensifies the processes of viscous and diffusional flow at the particle interfaces. 3. Powders of smaller particle size, too, being characterized by larger specific surface and greater particle structure defectiveness, exhibit intensified sintering.