A new method is presented for interpreting the data collected using three-electrode configurations, working electrode (WE), counter electrode (CE), and reference electrode (RE) in solid galvanic cells. The common flat arrangement of RE coplanar with the WE, both resting on the solid electrolyte (SE) is experimentally convenient but poses difficulties in the evaluation of the results. A calibration method is presented that allows one to relate the true impedance to the measured signals. It is also shown that in the special case where the RE is placed on a thinner extension of the SE, the placement of the reference electrode side by side introduces only a negligible error. In the case when the current carrying electrodes can be made of equal size, only misaligned, the error can be corrected, to first order, by an averaging procedure, using an annular reference electrode. The configuration analyzed in detail is a 2D one with partial results also reported for a 3D configuration. (C) 2008 Elsevier B.V. All rights reserved.