The paper presents the analysis of the aniline electropolymerization process by a recently developed experimental technique-dynamic electrochemical impedance spectroscopy. The process of the polyaniline first redox transformation was chosen for a detailed investigation. The technique used allowed to obtain the momentary impedance spectra for the potentiodynamic electrochemical reaction. The spectra were further analysed using the proposed electrical equivalent circuit. Thus, we were able to trace the electrochemical properties of the investigated system for potentiodynamic process. Results were in agreement with the expectations and confirmed the electrochemical nature of the analysed process. (C) 2004 Elsevier Ltd. All rights reserved.