Abstract: A process and a device for determining the moisture content of the material of a test object using microwaves. The properties of a resonator such as resonance frequency, resonance half-width value and amplitude of the resonance can be measured using a digitally tunable quartz-stable PLL-controlled microwave generator. By special processing of the variations in the results due to detuning of the resonator when it is being filled with a product, the moisture content of the material in the product can be measured exactly, independently of the density of the material and largely independently of the type of material and of changes in additives. The same measurement equipment can be used, without any rearrangement of the hardware, both in the ppm range and up to moisture contents greater than 80%. In addition, there are no special requirements concerning the shape of the sample.