A theoretical, two-dimensional, along-the-channel model has been developed to design fuel channels for proton exchange membrane (PEM) fuel cells. This has been implemented by solving the resultant ordinary differential equation with a straightforward shooting computational scheme. With such a design tool, an analysis can be made of the effects due to some operation and design parameters, such as inlet velocity, inlet pressure, catalyst activity, height of channel, and porosity of gas-diffusion layer to obtain a fuel cell with high performance. Present results indicate that there is always a trade-off between higher power density and higher efficiency of the fuel cell. Namely, a design for higher power density (a better performance) is always accompanied with a higher fuel efficiency (or a larger fuel consumption rate and a higher fuel cost), and vice versa. When some relevant physical parameters are determined experimentally and applied in the present model, a quantitative design for a fuel cell of either high efficiency or high performance is feasible. (C) 2003 Elsevier B.V. All rights reserved.