The operating conditions of a direct methanol fuel cell (DMFC) are important with regard to the power output and the efficiency of the cell. Especially the methanol concentration influences the overpotentials of both the anode and the cathode. Furthermore, the efficiency depends on the amount of methanol losses due to methanol permeation. The goal of this paper is to investigate the anode, the cathode and the methanol permeation of a DMFC experimentally to obtain a set of parameters for a DMFC model. The developed model predicts the U/I characteristics as well as the methanol permeation for different operating conditions. (C) 2004 Elsevier B.V. All rights reserved.