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Either an iridium electrode that was anodically pretreated or a glassy carbon electrode that was coated with a film that contained iridium oxide promoted the oxidation of hydrogen peroxide. With flow injection methodology, linear calibration curves were obtained over the 2 × 10−5 −3.6 × 10−8M range with 0.1M KOH as the carrier. With solutions of pH ⩾ 11, oxidation occurred at applied potentials of near 0.0 V vs. SCE, which is much lower than potentials needed at bare Pt or glassy carbon. The low overpotential suggests applications to systems where oxidation of other species limits the use of bare electrodes. Cyclic voltammetric studies show that HO2− is the electroactive species and that catalysis rather than mediation promotes the charge transfer. Dissolved oxygen does not interfere with the measurement.