Abstract: The presently claimed invention relates to a method of producing, in large volumes and at low cost, transition metal carbide, nitride or carbonitride whiskers, preferably submicron, having excellent reinforcing properties. These whiskers are suitable for use as a reinforcement in a wide range of materials, including metals, intermetallics, plastics, ceramics and metallic bonded hard material. The basic idea is the use of a carbon source with a volatile part which volatiles at temperatures up to 1000.degree. C. Transition metal oxide or alkali compounds thereof in amounts to satisfy the stoichiometric requirements of the desired carbide or nitride is mixed with the carbon powder along with an alkali metal chloride powder as a volatilization agent for the metal and a catalyst for the whisker growth such as Ni or Co. The reactant powders are blended in some typical manner using a high speed blender so as to intimately mix them.