We construct atomistic models of the Si(100)-SiO2 interface in accord with available experimental data. Combining classical and first-principles simulation methods, we generate transition structures from crystalline silicon to disordered SiO2. The generation procedure accounts for the density of coordination defects, the amount and location of partially oxidized Si atoms, and the mass density profile, as measured in electron-spin-resonance, photoemission, and x-ray reflectivity experiments, respectively. A variety of model interfaces are obtained, differing by the degree of order in the transition region. (C) 2003 American Institute of Physics.