An integrated fuel reformer and fuel cell system for microscale (10-500 mW) power generation is being developed and demonstrated as an alternative to conventional batteries. In this system, thermal energy is transformed to electricity by stripping the hydrogen from the hydrocarbon fuel (reforming) and converting the hydrogen to electricity in a proton exchange membrane (PEM) fuel cell. The fabrication and operation of a mesoscale fuel cell based on phosphoric acid doped polybenzimidazole (PBI) technology is discussed, along with tests integrating the methanol processor with the fuel cell. The PBI membrane had high ionic conductivity at high temperatures (>150 degreesC), and sustained the high conductivity at low relative humidity at these temperatures. This high-temperature stability and high ionic conductivity enabled the membrane to tolerate extremely high levels of carbon monoxide up to 10% without significant degradation in performance. The combined fuel cell/reformer system was successfully operated to enable the production of 23 mW of electrical power. (C) 2004 Elsevier B.V. All rights reserved.