The positive column of a glow discharge is placed along the axis of a cylindrical cavity excited in the TM010mode. The transmission of 3‐cm waves through the cavity and the shift in resonant frequency are observed as a function of discharge current. It is shown that from these measurements values of the complex conductivity, &sgr;r+i&sgr;i, of the electron gas can be calculated. Curves of the measured conductivity components as functions of pressure and current are given. Using a theoretical formula for the conductivity (see reference 6) values of electron density can in turn be calculated from both &sgr;rand &sgr;i. Langmuir probe studies are carried out to check the results obtained, and adequate agreement is found.