A fuel cell was developed using borohydride solutions as the fuel. The cell consisted of an anode made of a Zr-Ni alloy, a cathode made of Pt/C, and a Na+ form Nafion membrane as the electrolyte. The borohydride-fueled cell showed an open-circuit voltage of 1.3 V, compared with 1.0 V for a hydrogen gas-fueled one. The anode exhibited a small polarization property compared with the cathode. The cathode polarization was the main reason for the cell voltage drop with increasing currents. When a Nafion membrane was used as the electrolyte, it was confirmed that cations (Na+) were the charge carrier in it. Compared with Nafion 112 membrane, Nafion 117 membrane demonstrated a considerable resistance to borohydride crossover and resulted in acceptable cell performance. However, there are several problems such as H-2 evolution during operation, BH4- crossover, NaOH accumulation at the cathode, and NaBO2 accumulation at the anode in recent systems. Further effort is needed to develop the fuel cell using borohydrides as the fuel. (C) 2003 The Electrochemical Society.