Abstract: Electrocatalytic oxidation of ascorbic acid(AH₂) in acidic solutions was studied at electrodes coated with conducting polypyrrole(PP) films. Shifts of 200-300mVfor the oxidation potential of AH₂ at the polymer-coated electrodes were observed by cyclic voltammetry. Through measurements of Tafel plots, the mechanism of electrocatalytic oxidation of AH₂ was discussed. With the help of XPSand in-situ ESRspectrum, interactions between electrochemically oxidized PPand AH₂ surface species were also discussed.Acoupling of electron-transfer-mediated catalysis and chemical catalysis on PPwas believed.