Poly(3-octylthiophene) (POT) is an electrically conductive polymer in its oxidized forms. The oxidation-reduction (doping-undoping) process of the electrochemically synthesized polymer was studied by cyclic voltammetry. Different oxidation (doping) levels of POT result in different properties of the polymer electrode. The relative changes in conductivity when going from neutral to reversibly oxidized and finally to irreversibly oxidized POT were followed by resistance measurements. The electrolyte effects were analysed and new factors due to electropolymerization and doping processes determining the electrode properties were found. The electrochemically synthesized POT was found to be insoluble in chloroform.