Impedance spectroscopy is applied to characterize the porous microstructure of NiO-YSZ composites for solid oxide fuel cells after the pores are filled with a highly conductive aqueous medium. The apparent electrical characteristics are combined with conventional electrocomposite theory to describe the whole system, namely, a high resistivity component of an NiO-YSZ composite phase and a low resistivity component of a liquid phase, infiltrating the pores of the NiO-YSZ system. The resultant electrical information is probably due to the ionic conduction through the liquid phase within the pores of the NiO-YSZ composites. Image analysis is applied in order to characterize the microstructure of the NiO-YSZ composites. Furthermore, to determine the interconnectivity of the pores in the NiO-YSZ composite, which is a key microstructural factor, the microstructural information is combined with the electrical characteristics obtained through impedance spectroscopy. The interconnectivity of the pores is found to be lower than that estimated from two-dimensional image analysis. (c) 2005 Elsevier B.V. All rights reserved.