The operation of proton exchange membrane fuel cells (PEMFC) is highly dependent on operating conditions including humidity and feed ratio between the hydrogen and air streams. This work focuses on the effect of these parameters on the performance of a PEM fuel cell. We have employed traditional current density measurements to observe reduced power production at low feed humidity and low air:hydrogen feed ratios. Current experimental work is focused on employing electrochemical impedance spectroscopy (EIS) to understand specific resistances at various regions of the fuel cell. We perform EIS on a fuel cell with a Nafion 117 membrane, temperature between 35 – 50^oC, feed humidities ranging from 12 – 95+%, and feed ratios (air:H₂) from 2:1 up to 9:1. These varying conditions will allow us to separate transport steps related to humidity and feed ratios. The results from these experiments will be compared with equivalent circuit models and molecular modeling to better understand transport limitations throughout the fuel cell.