A performance enhancing break-in method for a proton exchange membrane ("PEM") fuel cell (12) includes cycling potentials of an anode electrode (14) and a cathode electrode (16) from a first potential to a second potential and back to the first potential, and repeating the cycling for each electrode (14, 16) for at least two electrode cycles. The potential cycling may be achieved in a first embodiment by applying a direct current from a programmable direct current power source (80) to the electrodes. Alternatively the potential cycling may be achieved by varying reactants to which the anode and cathode electrodes (14, 16) are exposed.