The impedance and offset potential of six disposable and two non-disposable electrodes were measured on 80 subjects. A total of 160 measurements were made on skin prepared by wiping with alcohol or acetone. For 640 measurements the skin was prepared by lightly sanding. The sanding of the skin reduced the impedance by a factor of approximately 50 for males and 100 for females. The offset potential for sanded skin was reduced by approximately 2. The performance of the disposable electrodes showed no great practical difference when applied on sanded skin. The median impedance ranged from 1500 to 3250 ohms. The median offset potential ranged from 0.5 to 4 mV. It was shown that a small DC current of 100 nA applied to stainless steel electrodes could cause a polarization voltage of approximately 0.5 volts to appear in 25 min.