Steady‐state creep of polycrystalline sodium choride having grain size stabilized by the addition of an aluminum oxide dispersion and containing about 4% porosity was investigated at 740°C over a range of grain sizes from 65–130 &mgr; and at stresses from 2.1–8.4 kg/cm2. Deformation was viscous (strain rate directly proportional to stress) at a rate in good agreement with the Nabarro—Herring equation, assuming the deformation rate to be limited by chlorine ion diffusion. Grain‐size dependence and absolute creep rates were satisfactorily predicted with Laurent and Be´nard's diffusion data, including the influence of grain size on diffusion coefficients.