It is shown that the electrode impedance can be separated from the bulk impedance in semiconductors and electrochemical cells using high dc biases. This is true both for two‐point dc resistance measurements and for two‐point ac impedance measurements. Experimental evidence on semiconductor thin films is presented. The dc biases required may be high, in the 50 V range, and can then be applied mainly to high resistance samples, in particular to thin films. ©1995 American Institute of Physics.