A simple approximate calculation method is given which permits determina-tion of the maximal scan rates of potential allowable for distortion-free recording of current-voltage curves with X-Y recorders. For the calculations only the response time of the recorder, the wave shape and the scan rate of potential need be known. Stationary mercury electrodes and rapid polarography with a dropping mercury electrode at controlled drop times were examined. Electroanalytical implications are discussed, with particular emphasis on the rapid a.c. polarographic method with short controlled drop times and on stationary-electrode fundamental and second harmonic a.c. voltammetry. Theoretically and experimentally it has been shown that an X-Y recorder with 0.5-1.0-s response time can be used for scan rates up to about (50/nt') mV s-1 with a.c. techniques and about (100/nt') mV s-1 with d.c. polarography (t'= response time of recorder, n = number of electrons).