The demands for greater efficiency and reduced environmental pollution are two of the main factors behind the intense research and development for new and improved materials for propulsion and power generation systems. On the grounds of density and retention of properties at high temperatures, ceramics are attractive alternatives to metallic materials. While much attention is focused on the problem of mechanical reliability, the question of corrosion resistance, and more importantly the synergism between corrosion and strength, are critical factors affecting the life of components. This investigation addresses the corrosion of a Si3N4, hot-pressed with 3% Al2O3 and 8% Y2O3, in a combustion atmosphere paying particular attention to corrosion. The results show that the dominant surface reaction in an atmosphere containing SO2 and compounds of sodium was oxidation, giving a surface product of silica, but the kinetics were in some cases not parabolic as often reported. It was also shown that strength progressively decreased with Increasing corrosion test temperature, probably due to the formation of subsurface defects.