Poly(aniline-co-o-aminophenol) (PAN-OAP) has been synthesized by electrochemical copolymerization of aniline (AN) and o-aminophenol (OAP) on glassy carbon electrode (GCE). FT-IR, UV-vis and electrochemical characterizations indicate the formation of the PAN-OAP and it has the structure of a head-to-tail coupling of AN and OAP units. When the concentration ratio of OAP-AN is more than 1:20, the voltammetric behaviors for the copolymerization of AN and OAP are similar, while the copolymerization rate decreases with increasing of OAP concentration in the solution. The PAN-OAP can maintain its electroactivity in neutral and even in alkaline media, although the electroactivity of the copolymers decrease with increasing of the concentration ratio of OAP-AN in solution. The PAN-OAP film coated GCE exhibits excellent electrocatalytic responses towards the electro-oxidation of ascorbic acid (AA) in phosphate buffer solution of pH 6.8. The anode peak potential of AA shifts from 0.53 V at bare GCE to 0.21 V at PAN-OAP/GCE with greatly enhanced current response. A linear calibration graph is obtained over the AA concentration range of 5 x 10(-4) 1.65 x 10(-2) mol L-1 using cyclic voltammetry. Chronoamperometry has also been employed to investigate the electro-oxidation of AA. The PAN-OAP/GCE shows good stability and reproducibility. (C) 2007 Published by Elsevier B.V.