This paper describes a novel electrochemical method for the generation of HO2- using an alkaline fuel cell (AFC). The system is formed by an undivided cell containing a H-2-diffusion anode, an O-2-diffusion cathode, and a KOH solution as electrolyte. It can work in batch or in continuous mode, cogenerating electricity and HO2-, which is formed from the two-electron reduction of O-2 at the cathode. The evolution of cell voltage, current density, HO2- production, and current efficiency with time have been determined when the electrolyte remains quiescent, recirculates through the cell, or is continuously injected to it. This last device yields the best operative parameters, allowing current densities of 130 mA cm(-2) and current efficiencies close to 100% using 1 mol dm(-3) KOH at 20 degrees C. The effect of HO2- upon the anodic and cathodic reactions has been studied by linear sweep voltammetry. Adsorption of this species on the cathode can explain the loss of performance of the AFC with working time using a quiescent electrolyte or under recirculation conditions. The O-2-diffusion cathode and the AFC showed good reversibility when the cell contained a fresh KOH solution with HO2-.