The distribution of carbon monoxide (CO) across the anode of a polymer electrolyte fuel cell with a single channel flow-field is modelled and compared with experimental results obtained using localised stripping voltammetry. Good agreement is observed between experiment and model over a wide range of CO carrier gas flow rates. The model is used to predict the effect of CO transient poisoning, expected to occur during system start-up, when high CO slippage is likely to occur from the fuel processor and the fuel cell is not electrically loaded. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.