We have determined the relative stability of stoichiometric, oxygen-rich, and aluminum-rich Al/Al 2O (3) and Ag/Al 2O (3) interfaces from first principles. Stable structures vary significantly with oxygen chemical potentials. Computed works of adhesion agree reasonably well with sessile drop experimental values, including correlation with measured oxygen chemisorption effects on Ag. The ordering of predicted bond energies of the interfaces, ceramics, and metals seems consistent with monotonic and fatigue fracture experiments.