We describe an original and easy method to measure the microwave conductivity of semiconductors as a function of frequency (up to 140 GHz) and high electric field. This method does not need impedance measurements of the semiconductor and is based on the comparison of thermal and high field effects; measurements are equally possible as a function of lattice temperature. It may be used with sufficiently low‐doped semiconductor materials. In the case of silicon, measurements are possible for 1 <pDC<50 &OHgr;cm. An example of results is given for 10 &OHgr;cm n‐Si at 300 K and for frequencies equal to 10, 35, and 70 GHz.