The atomic structure of amorphous Al2O3 has been determined using a molecular dynamics simulation. The local electronic structures of the simulated amorphous structure and of the crystalline structure of Al2O3 were investigated using first principle cluster calculations. The calculated partial densities of states for the two structures are compared with their photoelectron spectra. We find that there is a local oxygen deficiency around Al atoms in amorphous Al2O3, which results in a different local electronic structure in amorphous Al2O3. We also show with our calculations and photoelectron spectroscopy that Al2O3 thin films have both crystalline and amorphous properties. (C) 2004 Elsevier B.V. All rights reserved.