A reaction-bonding process, which offers low sintering shrinkage and is a low-cost process, was applied to fabricate Y-alpha-SiAlON ceramics. The green compacts composed of Si, Y2O3, Al2O3, and AlN were nitrided and subsequently postsintered. Dense single-phase Y-alpha-SiAlON with elongated grain morphology could be achieved in the specimen postsintered at 1900degreesC. The material exhibited high hardness (1850 HV10) and high fracture toughness (5.1 MPa(.)m(1/2)).