Finely divided insoluble solid particles stabilize emulsions primarily by providing steric hindrance to the coalescence of emulsion droplets. The effectiveness of these particles in stabilizing emulsions depends largely on the formation of a stable viscoelastic monolayer of solid particles at the oil-water interface that can inhibit the coalescence of emulsion droplets. Here we present a model to describe the rheological properties of fluid-fluid interfaces containing colloidal particles. It is shown that at sufficiently high concentrations of particles, colloid-laden oil-water interfaces exhibit viscoelastic behavior. Such viscoelastic interfaces enhance emulsion stability by decreasing the rate of film thinning between coalescing emulsion droplets.