This International Standard relates to a measurement method for complex permittivity of a dielectric rod at microwave frequency. This method has been developed to evaluate the dielectric properties of low-loss materials in coaxial cables and electronic devices used in microwave systems. It uses the TM010 mode in a circular cylindrical cavity and presents accurate measurement results of a dielectric rod sample, where the effect of sample insertion holes is taken into account accurately on the basis of the rigorous electromagnetic analysis. In comparison with the conventional method described in IEC 60556 [2], this method has the following characteristics: • the values of the relative permittivity ε' and loss tangent tand of a dielectric rod sample can be measured accurately and non-destructively; • the measurement accuracy is within 1,0 % for ε' and within 20 % for tand; • the effect of sample insertion holes is corrected using correction charts presented; • this method is applicable for the measurements on the following condition: – frequency: 1 GHz ≦f ≦10 GHz; – relative permittivity: 1 ≦ε' ≦100; – loss tangent: 10–4 ≦tand ≦10–1.