The effects of different operating parameters on the performance of proton exchange membrane (PEM) fuel cell have been studied experimentally using pure hydrogen on the anode side and air on the cathode side. Experiments with different fuel cell operating temperatures, different cathode and anode humidification temperatures, different operating pressures, and various combinations of these parameters have been carried out. The experimental results are presented in the form of polarization curves, which show the effects of the various operating parameters on the performance of the PEM fuel cell. The possible mechanisms of the parameter effects and their interrelationships are discussed. In addition, a comprehensive three-dimensional fuel cell model is briefly presented and the modeling results are compared with our experimental data. The comparison shows good agreements between the modeling results and the experimental data. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.