Carbothermal reduction and simultaneous nitriding (CTRN) of natural aluminosilicates is a method used to obtain phases of Si-Al-O-N system. SiAlON phases have important applications, such as high technology ceramics, for wear parts, cutting tools or special purpose refractory materials. In this study carbothermal reduction and nitriding reactions of kaolinite obtained from Balikesir-Duvertepe area of Turkey were studied. The mean particle sizes of kaolinite used for CTRN process were 6.4, 4.67, and 2.29 m, respectively. The reactions of kaolinite and carbon black mixture carried out at 1400 degrees C for 2, 4, and 8 h. CTRN process was conducted in an atmosphere controlled tube furnace in nitrogen flow of 4 cm(3)/min. All products were examined by XRD and SEM to determine the transformation, morphology and chemical composition. The results showed that the most of SiAlON transformations occurred at 1400 degrees C for 8 h. It was observed that when decreasing the mean particle size of the starting material the transformation of kaolinite to SiAlON was increased.