A proton exchange membrane fuel cell combined heat and power system has been chosen as a platform on which key components and system integration technologies have been developed to advance the applications of fuel-cell technology. The prototype system consists mainly of a fuel-cell stack, a natural gas reformer to supply hydrogen-rich reformate gas to the stack, a power conditioner to convert and invert the electricity generated by the stack, and a water and heat management network to provide the oxidizer (air) to and necessary cooling and humidification for the stack. The design of the stack and its components, catalysts development, design and testing of the natural gas reformer, were studied. In addition, the durability of a CO tolerant membrane-electrode-assembly has been studied with the assistance of air bleeding. Preliminary testing of the prototype combined heat and power system was carried out. It was found that the maintenance of a uniform output voltage across all single cells was more difficult with reformatted gas rather than using pure hydrogen. It was also found that the design of water and heat management network played an important role in the overall efficiency of the system.