The electrochemical synthesis of polyindole upon anodic oxidation of indole (C8NH7) in dichloromethane (CH2Cl2) containing 0.1 M tetrabutylammonium perchlorate (TBAP) is reported. The air-stable polyindole films were obtained by sweeping the potential between -0.2 and 1.0 V vs Ag/AgCl as well as at constant potential (1.0 V vs Ag/AgCl) and constant current (0.2-0.3 mA/cm(2)). The conductivities of such films were found to lie in the range 0.1-1 S cm(-1). The behavior of the polymer was studied by cyclic voltammetry and chronoamperometry. The electrochemically produced polyindole was studied as active material for secondary batteries in aqueous electrolyte. A Zn/1 M ZnSO4/polyindole cell gave a maximum capacity of 90 Ah kg(-1) and an open-circuit potential (V-oc) of 1.45 V. This battery showed good reversibility and good coulombic efficiency.