An electrolytic cell and process for the simultaneous production of hydrogen peroxide and hypochlorous ion. The electrolytic cell has an anode chamber housing an insoluble anode capable of oxidizing halide ion, a cathode chamber housing a gas diffusion cathode capable of oxidizing an oxygen-containing gas to produce hydrogen peroxide, a membrane separating the anode and cathode chambers, and means for supplying water containing halide ion to the anode chamber and an oxygen-containing gas and an electrolyte to the cathode chamber, whereby hypohalide and hydrogen peroxide are produced in the anode chamber and the cathode chamber, respectively. Also disclosed is a process for treating water using the electrolytic cell.