MoO3 powders with plate particles have been prepared by heating hexaammonium heptamolybdate tetrahydrate ((NH4)(6)Mo7O24 . 4H(2)O) for 1 h at 650 degrees C. Densification has been performed by hot pressing for 2 h at 630 degrees C and 30 MPa. Grain-oriented MoO3 ceramics (>98% of theoretical) are fabricated, in which the [010] axis is parallel to the hot pressing direction. Their electrical conductivities have been measured in the temperature range of 100 degrees to 600 degrees C. Sintered MoO3 is a ceramic semiconductor. Activation energies are determined to be 0.49 and 0.76 eV for initial and final stages, respectively.