This part of IEC 61338 describes the dielectric rod resonator measurement method for a wide range of microwave dielectric properties in practical applications. This method has the following characteristics: – a complete and exact mathematical solution of complex relative permittivity is given by easy computer software; – the measurement error is less than 0,3 % for ε′ and less than 0,05 × 10–4 for tan δ; – the TCF is directly measured without any compensation with a measurement error less than 1 × 10–6/K. The object of this standard is to describe the measurement methods of the complex relative permittivity of dielectric resonator materials at microwave frequencies by means of the dielectric rod resonator method short-circuited at both ends by parallel conducting plates. The measuring parameters are ε′, tan δ, TCF and the temperature dependence of tan δ at the resonance frequency. The dielectric materials are assumed to be isotropic and homogeneous.