Sodium/nickel cells have high energy density and are developed as a power source for electric vehicles. A microtomograph was used in order to determine the inner structure of a commercial ZEBRA cell after fabrication. The tomograms represent the absorption density in a slice 0.05 mm thick. The different gray values of the tomogram allow the identification of different material classes: air, sodium, alumina or sodium chloride, porous nickel chloride, and solid nickel. It was found that the structure of the cathode of nickel chloride is dependent on the charging state and the height inside the cell. Tomographic imaging of such cells may serve the purposes of imaging of material changes at operating temperatures and quality control during fabrication. (C) 2001 The Electrochemical Society. All rights reserved.