The present study is focused on the optimization of the proton exchange membrane fuel cell (PEMFC). A simplified conjugate-gradient method (SCGM) is employed to seek the optimal combination of the design parameters, including the channel width ratio (lambda), the porosity of GDL (epsilon(GDL)), and the porosity of the catalyst layer (epsilon(Cat)). In this report, the concept of the method is described in detail and the results of the optimization process are discussed. The results show that the present approach is capable of providing an optimal design under specific operation conditions. (c) 2006 Elsevier B.V. All rights reserved.