The influence of changing humidification conditions in polymer electrolyte membrane fuel cells (PEFC) was investigated by current density distribution measurements. It is well known that the performance of fuel cells strongly depends on the humidification state of the membrane-electrode assembly (MEA) by the alteration in the membrane resistance and the alteration of transport pro¬cesses in the electrodes. During reduction of the humidification of the operation gases of a PEMFC single cell with an active surface area of 23 cm2 at potentio-static conditions the current decreases from over 14 A to 0.4 A. The local current density measurement indicates the change of the shape of the current density distribution. The maximum in the local current density shifts from the middle of the cell to the gas outlet for the oxygen; during the re-humidification the shift of the maximum position in the current density distribution is significantly lower.