This paper presents the utilization of a supercapacitor as an auxiliary power source in a distributed generation system, composed of a polymer electrolyte membrane fuel cell (PEMFC) as the main energy source. The main weak point of fuel cells (FCs) is slow dynamics because one must limit the FC current slope in order to prevent fuel starvation problems, to improve its performance and lifetime. The very fast power response and high specific power of a supercapacitor can complement the slower power output of the main source to produce the compatibility and performance characteristics needed in a load. The FC and supercapacitor characteristics are clearly presented. Experimental results with small-scale devices (supercapacitor bank: 292-F, 30-V, 400-A; PEMFC: 500-W, 40-A) illustrate excellent performance during a motor drive cycle.