In this study, the effects of operation conditions on the performance of a polymer electrolyte membrane fuel cell are investigated and the results are presented together with a comprehensive literature review on the related topics. The cells with 25 cm2 active area are tested for different inlet gas humidification levels and inlet temperatures, operating temperatures and oxidant type. The cells are characterized by the performance curves together with the cell resistance measurements. The results indicate that the humidification of the inlet gases positively affect the cell performance. However, the improvement in thecell performance is higher when the cathode gas is humidified. In addition, the operating temperature and the inlet gas temperatures are found to be the most significant parameters. The cell performance tends to increase significantly with increasing the operating and inlet gas temperatures. The effect of the oxidant type is also considered and the cell tested with pure oxygen shows slightly higher performance.