A simple method for synthesis of beta-SiAlON powder by nitridation of alumina-silica gel in ammonia was provided. Precursor was obtained from a mixture of nanosized alumina and colloidal silica. Nitridation reactions took place at 1100 degrees C and conversion to beta-SiAlON was achieved at 1300 degrees C for 2-3 h. The synthesized beta-SiAlON powder was nanocrystalline in size (<100 nm).