This paper presents a general model for air-side feed stream contamination that has the capability of simulating both transient and steady-state performance of a PEM fuel cell in the presence of air-side feed stream impurities. The model is developed based on the oxygen reduction reaction mechanism, contaminant Surface adsorption/desorption, and electrochemical reaction kinetics. The model is then applied to the study of air-side toluene contamination. Experimental data for toluene contamination at four current densities (0.2,0.5,0.75 and 1.0cm(-2)) and three contamination levels (1, 5 and 10ppm) were used to validate the model. In addition, it is expected that, with parameter adjustment, this model can also be used to predict performance degradation caused by other air impurities such as nitrogen oxides (NOx) and sulfur oxides (SOx). Crown Copyright (c) 2008 Published by Elsevier B.V. All rights reserved.