This report describes the design, fabrication and testing of a 25kW phosphoric acid fuel cell system aimed at stationary applications, and the technology development underlying that system. The 25kW fuel cell ran at rated power in both the open and closed loop mode in the summer of 1988. Problems encountered and solved include acid replenishment leakage, gas cross-leakage and edge-leakage in bipolar plates, corrosion of metallic cooling plates and current collectors, cooling groove depth variations, coolant connection leaks, etc. 84 figs., 7 tabs.