The MgO films grown on amorphous SiO2 by electron-beam evaporation were investigated. The films with columnar microstructures were mainly with a(111)preferred orientation. The MgO crystallites near the MgO/SiO2 interface were very fine, which means a high nucleation rate at the initial stage of the film growth. The grains formed at the initial growth stage became less (111) oriented with increasing deposition temperature. Instead, the (100) texture came to be enhanced. There occurred a somewhat abrupt change in the grain size at the film thickness of 450 to 700 Angstrom. The (111) texture prevailed over other orientations above that film thickness, regardless of the deposition temperature.