To develop a technology for synthesizing transparent polycrystalline alumina ceramic by controlling the grain size in the range of nanometer level. The experiment concentrated on the effects of forming and sintering conditions on the transparency and grain size. Alumina powder (TMDA) of nanometer size was used as starting material. The alumina powder was mixed with MgO ranging from 0-0.1 wt%. Alumina bodies were formed by both cold isostatic press (CIP) and gel casting using agar as the gelling additive. The green bodies were sintered at 1250 to 1550 ํC for 2 h both in air and under vacuum followed by hot isostatic pressing (HIP) at 1250 and 1300 ํC for 2 h under ar pressure of 150 MPa. Alumina ceramic doped with MgO formed by CIP method and sintered under vacuum at 1450 to 1550 ํC was translucent, while MgO-free alumina ceramic was opaque. On the other hand, both MgO-free and MgO doped alumina ceramic sintered in air were opague. Nanometer sized grain was achieved at the sintering temperature lower than 1350 ํC. Specimen pre-sintered in air atmosphere followed by hot isostatic pressing became transparent. On the other hand, specimen pre-sintered under vacuum was translucent and still showed gray color. Alumina ceramics formed by gel casting showed transparency. However, alumina ceramics formed by CIP method showed transparency better than that formed by gel casting method.