In the project RMT-monitoring funded by the European Union, a new radiomagnetotelluric device has been developed which can record time series of electric and magnetic fields in a wide frequency range from 10 kHz to 1 MHz. Transfer functions are determined by spectral analysis using a newly developed processing software. A workbench program has been developed in which the transfer functions are interpreted with conductivity models based on new inversion algorithms. <br>The developed tensor radiomagnetotelluric device was tested in the laboratory and then applied successfully in the field to several environmental and groundwater problems in Russia, Ukraine, Denmark, Romania, and Germany. <br>The observed transfer functions in the field are the first ones worldwide in the frequency above 250 kHz which leads to a better resolution of the shallow structure. The new device enables quick and efficient mapping of polluted areas and supports tensor measurements allowing a 2D or 3D interpretation of the field data.