An extension of the Nernst-Planck-Poisson (NPP) formulation is developed to include the effects of stress in modeling mixed ionic-electronic conducting (MIEC) ceramics. In addition to diffusion and migration contributions, the Nernst-Planck flux includes the effects of hydrostatic stress gradients on the transport of charged defects. The model uses a thin-plate formulation to determine hydrostatic stress profiles, which depend on the defect-concentration profiles. With oxygen-separation membranes in mind, the model is illustrated using a combination of measured and estimated material properties for La0.6Sr0.4Co0.8Fe0.2O3-delta (LSCF6482). Under transient conditions, where the oxygen partial pressure on one side of a membrane is suddenly changed, the model predicts concentration and stress profiles. The predicted maximum tensile stress can be very high, suggesting the possibility for membrane damage or failure. (C) 2016 The Electrochemical Society. All rights reserved.