beta-SiAlON was synthesized from Y-type zeolite and its formation mechanism was determined using magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy and powder X-ray diffraction (XRD). Y-type zeolite and carbon powders were mixed for 36 h, fired at 1050 degrees to 1450 degrees C for 0-2 h in flowing gas (0.5 L/min N-2), then heat treated at 700 degrees C for 2 h in air to remove residual carbon. The resulting product was, according to XRD analysis, mono-phase beta-SiAlON; but minor amounts of unreacted SiO2 and SiC (possibly amorphous) were detected in the NMR spectra. It was found that beta-SiAlONs with higher and lower Z values are formed by different reaction pathways.