A two-dimensional model of a single-channel polymer fuel cell has been developed. To achieve model validation, current mapping experiments were performed on the cathode side of a single-channel polymer electrolyte fuel cell (PEFC) of various channel widths, at different reactant flow rates and over a range of operating cell voltages. The fuel side was operated in cross-flow mode, with a high stoichiometric excess of hydrogen to ensure no limitations in anode performance as a function of position along the channel. The solution domain comprises seven regions, (two inlet channels, two diffusers, two active catalyst layers, and a membrane) and considers transport of hydrogen and water vapor in the anode and oxygen and nitrogen and water vapor in the cathode. The resulting set of coupled differential equations was solved numerically with , a -based software. The model has been compared to data from a single-channel PEFC, and good agreement between experiment and theory was obtained.