A model based on defect chemistry has been developed to describe the creep behavior of La0.2Sr0.8Fe0.8Cr0.2O3-delta. The model is based on partial clustering of divalent B site cations and oxygen vacancies. According to the model, the increased strain rates at low p(O2) are due to increased mobility of B site cations in linked clusters. The cluster concentration is proportional to the oxygen partial pressure, p(O2)(m) with m = -1/2 in accordance with the creep data. The model describes the creep behavior in the entire p(O2) range used in the measurements. Models based on random non-interacting defects or including ambipolar diffusion, strontium segregation or partial decomposition cannot give the observed p(O2) dependence of the creep behavior. (C) 2004 Elsevier B.V. All rights reserved.