Carbothermic reduction of zircon powders has been studied under argon and nitrogen gas pressures of 0.15 MPa in order to obtain biphasic composite powder mixtures containing zirconia and silicon carbide whiskers. The reduction has been carried out using different mole ratios of carbon and zircon. Carbon was used in the form of activated charcoal (specific surface area similar to 1000 m(2) g(-1)) or carbon black (specific surface area similar to 300 m(2) g(-1)). Whilst complete decomposition to m-ZrO2 was obtained in the argon atmosphere at 1700 degrees C, under the nitrogen atmosphere the conversion was incomplete even at 1700 degrees C. However, the extent of conversion to zirconia at 1650 degrees C under nitrogen was found to be more than that under argon gas. In a few cases, particularly under the nitrogen atmosphere, minor amounts of other forms of zirconia e.g., tetragonal (t)-ZrO2 or orthorhombic (o)-ZrO2 were formed along with the major monoclinic (m)-ZrO2 phase. The rate of reaction was found in general to increase with an increase in the carbon content. The studies particularly indicate that activated charcoal is a better reducing agent than carbon black owing probably to its enormous surface area. Further, it was also noted that cobalt chloride and sodium chloride act as a catalyst and a space forming agent respectively. They aid silicon carbide whisker formation and growth and hence the reaction is appreciably accelerated and reaches completion at 1650 degrees C in the argon atmosphere.