An algorithm is described in which galvanostatic regulation of electrochemical impedance measurements is conducted with an amplitude of current perturbation that is adjusted at each frequency to yield a desired variation in potential. Measurements at previous frequencies are used to estimate the value of the impedance at the target frequency. The algorithm was implemented using LabView for Windows(R) on an IMB-compatible computer. Experimental results illustrate artifacts which can arise as a result of galvanostatic measurement with a fixed current amplitude or as a result of potentiostatic measurements for systems with a changing corrosion potential.