Thin epitaxial In2O3 films were grown on MgO(001) single crystal substrates by electron beam evaporation in a high-vacuum chamber. During the evaporation, the substrate was heated to temperatures between 600 and 850 degrees C, and different oxygen background pressures were applied. The films were first characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Structure, morphology and crystallographic orientation of the film and the MgO/In2O3 interfaces were then investigated by transmission electron microscopy/selected area electron diffraction (TEM/SAED), In all samples the major part of the film area grows with the In2O3(111) plane parallel to the MgO(001) surface, and shows an in-plane orientation with four domains occurring, characterized by the In2O3(<1(1)over bar 10>) plans being parallel to one of the four different MgO(110) planes. These parts of the In2O3 films consist of grains with a columnar structure, with a typical grain diameter of 50 to 200 nm for a film thickness ranging from 120 to 150 nm. and an extreme small rocking curve FWHM up to 0.1 degrees. A minor part of the film area was found in a "cube-to-cube" orientation : In2O3(001)parallel to MgO(001); In2O3[100]parallel to MgO[100]. The amount of thr minor part film area decreases with increasing substrate temperature down to lower than 0.3%.