The method of measurement of the dielectric properties of solid dielectrics described by S. Roberts and A. von Hippel has been applied with 3‐cm wave‐length waves in a rectangular wave guide. In this method the dielectric sample is placed at a short circuited end of the transmission line, and the dielectric properties of the sample, calculated from the position of a minimum of the standing wave and the ratio of the minimum field strength to the maximum field strength of the standing wave. A simplified procedure for calculating the dielectric properties from the measurements is presented. Values are given of the dielectric properties of some common plastic and ceramic materials at 10‐cm wave‐length and 3‐cm wave‐length, which were measured with this method.