The Nexa(TM) power module is evaluated at membrane-electrode-assembly (MEA) and stack levels. The I-V Curves of the Nexa(TM) PEM fuel cell system is measured using periodic current interruption to maintain isothermal stack temperature. The uniformity analysis is mainly performed on the load of 800 W for all MEAs in 10 individual Nexa(TM) stacks. Statistical data show that the MEA voltage without an external load averages 224 mV higher than that with a load of 800 W The MEA voltage difference is especially pronounced around the two cells at the air compressor side. The average difference is 8.8% and the highest difference is 13.1% between the minimum MEA voltage in the stack and the mean value. This voltage difference reveals a possibility to increase the product power capability and cut the cost per kilowatts by improving the weak performance electrodes or MEAs in the stack. (C) 2003 Elsevier B.V. All rights reserved.