Carbochlorination reactions of tantalum and niobium pentoxides represent am interesting route of extraction of tantalum and niobium from ores or minerals. Both reactions have not been systematically studied in the literature. The kinetic study reported here was carried out in a fixed-bed reactor in a temperature domain T = 800 - 1,000 degrees C. The products of the reaction under the conditions studied are in the gaseous phase. With CO as a reducing agent, the reactions in question are of the noncatalytic gas - solid type, and the experimental data fit the shrinking core model. When using carbon as a reducing agent, the reactions are of the gas - solid - solid type, and the reactivity is much higher than that using CO alone. A reaction model based on phase boundary control was used to process the experimental darn. Thermodynamic calculations revealed that at temperatures below 1,000 degrees C the carbochlorination reactions result in the corresponding pentachlorides.