Abstract: Tomographic images (I.sub.1 and I.sub.2) of a body are constructed by placing a plurality of surface electrodes (1 to 16) at spaced intervals on the body (M), causing currents to flow in the body, and measuring the potential between pairs of electrodes, calculating the potential in each case on the assumption that the body consists of one uniform medium, plotting the isopotentials corresponding to the calculated results to create a uniform image of the body, obtaining the ratio between the measured potential and the calculated potential in each case, and modifying the image in accordance with the respective ratios by increasing the impedance along an isopotential in proportion to a ratio greater than unity or decreasing the impedance in proportion to a ratio less than unity. The calculations of potentials and the obtaining of ratios are carried out using a computer and the plotting of the isopotentials is carried out by a visual display unit (VDU) and/or a print-out unit run off the computer.