A laboratory direct sodium borohydride/hydrogen peroxide (NaBH4/H2O2) fuel cell using platinum electrodes is studied at room temperature. Several polymeric ion-exchange membranes are considered as ionic separators for the cell. Cell voltages up to 1.84 V and short-circuit currents of 348 mA cm-2 are reported. In the absence of an electric field, reasonable cell stabilities are attained; in the presence of current, cell voltages drop quickly, limiting the cell operation to shorter duration times. Energy densities and specific capacities estimated for a 1 h-cell operation at 1 V are up to 1632 Wh kg-1 and 1632 Ah kg-1, respectively. A power density of about 96 mW cm-2 at a cell voltage of 0.6 V and at a current density of 160 mA cm-2 is reported for the cell using a Nafion 117 membrane, but these values cannot be sustained for appreciable operation times. The tested membranes are compared in terms of their effect on the performance of the NaBH4/H2O2 fuel cell.