Electrically conductive alpha-beta SiAlON composites containing 30 vol. % MoSi2 was prepared by gas pressure sintering (GPS). The effect of sintering atmosphere on phase formation, grain growth, mechanical and electrical properties of the composites was discussed. In order to understand the effect of sintering atmosphere, composites were sintered under N-2 and Ar atmospheres during gas pressure sintering. It was observed that MoSi2 particles transformed to Mo5Si3 under N-2 but not under Ar. The resistivity of the produced composites varied from 10(8) Omega.m to 10(-3) Omega.m depending on the sintering atmosphere and the phase composition.