Alumina specimens with small amounts of CaO and TiO2 were prepared and their microstructural evolution during sintering was investigated. Because of the appearance of a liquid phase during sintering, a duplex microstructure of a few abnormal grains and fine matrix grains was obtained when the CaO + TiO2 content was small (less than or equal to0.04 wt%). When the CaO + TiO2 content was relatively high (greater than or equal to0.1 wt%), many grains grew and impinged upon each other. As a result, a rather uniform and homogeneous microstructure was observed.