The interface between crystalline Si and its amorphous native oxide SiO 2 is the basis for most current computer technology; yet its structure remains poorly understood. Here, we summarize a recent computational approach to this problem, which explicitly averages over the ensemble of configurations of the amorphous oxide. The approach makes possible calculations of equilibrium interface structures and energies for an amorphous oxide interface. The resulting model for the Si-SiO 2 interface has low energy, and it reconciles a variety of puzzling experimental results.