A series of nitroxyl radicals have been used as efficient organic catalysts for the mediated oxidation of hydrogen peroxide at a carbon paste electrode immersed in aqueous media. Second order catalytic rate constants were measured and indicate an efficient inner sphere catalytic process. A nitroxide-loaded carbon paste electrode was prepared and used as a sensitive reagentless hydrogen peroxide sensor. The sensitivity of the resulting H2O2 anode was 0.23 A cm(-2) M-1 at 0.6 V and a detection limit of 5 X 10(-8) M was obtained.