Although a major amount of research has been undertaken on failure modes of fuel cell durability, relatively little research has been carried out on cationic contamination. One of the primary issues of cationic contamination is the low level of contaminant needed to impact a cell. The uptake of contaminant cations leads to dramatically decreased performance even at low levels of incorporation. Foreign cations replacing protons in the ionomer phase likely increase ohmic, kinetic, and mass transport losses in the cell and may alter cell thermodynamics. At this point in time, little is known about the rates of exposure, uptake, and escape of contaminant cations in operating fuel cells. The extent of performance loss following cationic contamination and recovery of performance after contamination are discussed in terms of cation contaminant impact on fuel cell durability.