In the present study, pressureless joining of gas pressure sintered (alpha-beta)-SiAlON ceramics to pyrex glass was investigated. Preoxidized SiAlON ceramics were used to enhance wettability and provide chemical compatibility of the components. Microstructure and chemistry of the joints were characterised by scanning electron microscopy (SEM) in combination with energy dispersive X-ray (EDX) spectroscopy. It was shown that chemical reactions took place at the interface region of the joined samples and as a result, phases were formed such as Y-aluminium silicate and cristobalite. Considering the well-known phase transformations of cristobalite at around 210degreesC, further studies were also undertaken to avoid cristobalite formation during joining.