A sinter-forging technique was successfully applied to fabricate a silicon nitride with a lutetia (Lu2O3) additive. The sinter-forged specimen had a strongly anisotropic microstructure where rodlike silicon nitride grains preferentially aligned perpendicular to the forging direction. The specimen exhibited superior strength of similar to700 MPa at 1500degreesC. This strength was highest when compared with previous silicon nitrides at temperatures > 1400degreesC. Such superior high-temperature strength was attributed to grain alignment as well as to the refractory grain-boundary glassy phase and the existence of glass-free grain boundaries.