The electrochemical polymerization of 3,4-ethylenedioxythiophene (EDT) was studied in microemulsions containing polyoxyethylene-10-laurylether as a non-ionic micellar surfactant. This allows to increase the solubility of the monomer in an aqueous solution. Thereby, the surfactant affects the transport of EDT. Capacity measurements and cyclic voltammetry on bare Pt show the influence of the surfactant by adsorption on the metal, too. An adsorption on the polyethylenedioxythiophene (PEDT) surface could not be proved. Combined charge transfer and diffusion limitations control the electropolymerization kinetics at low monomer and surfactant concentrations. Charge transfer becomes limiting at high EDT concentrations. Apparent diffusion coefficients and the charge transfer coefficient of the electrochemical reaction were obtained from RDE experiments. The redox activity, UV/VIS spectra and surface morphology (from SEM pictures) depend on the polymerization potential and the solution composition. Best films were obtained at low potentials in LiClO4. At high potentials overoxidation of the polymer takes place, but an incorporation of the surfactant could not be detected. (C) 2000 Elsevier Science Ltd. AU rights reserved.