The effects of different parameters on the performances of proton exchange membrane fuel cells were studied experimentally. Experiments with different fuel cell temperatures, humidification temperatures and backpressures of reactant gases have been carried out. Polarization curves from experimental data are presented and the effects of the parameters on the performance of the PEM fuel cell are discussed. The experimental data obtained in this work are used to validate our 3-D mathematical model. It is found that modeling results agree well with our experimental data.