The aim of the present paper was to determine the electrochemical state of the positive electrodes during the formation process using the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The investigations of typical positive electrodes were carried out for 12 states-of-electroformation (SOE). It was found that during electroformation the positive electrodes undergo dramatic changes which are reflected in EIS spectra. SOE strongly influences the equivalent electrical circuit and the range of impedance spectrum of non-inductive character. The obtained results showed that EIS technique can be used as a sensitive method allowing to distinguish the consecutive steps of electroformation. The conclusions drawn from EIS measurements are confirmed by CV measurements performed for selected SOEs. (C) 2003 Elsevier B.V. All rights reserved.