Abstract: An electrode arrangement for an electrical impedance tomography system comprises a plurality of electrodes in an array mounted in a support medium for supporting the electrodes adjacent a surface of a volume the electrical conductivity distribution of which is to be measured, for example the thorax or another body part, a pipeline, the ground, and so on. The electrodes are disposed in two groups, the arrangement being such that, in use, one group will be closer to the surface than the other group, In operation, applying a known current to them. For each stimulated pair, a resulting potential difference will be recorded at the pair of the remaining electrodes which, if stimulated, would produce an electric field with vectors of the electric field produced by the stimulated pair of electrodes.