A research program, sponsored by Istituto Superiore Poste e Telecomunicazioni and developed by Centro Onde Millimetriche of Fondazione Ugo Bordoni, is currently in progress in Italy, with the purpose of demonstrating the feasibility and of finding general design criteria for a circular waveguide telecommunication system. The C.O.M. has taken upon itself the investigation of the transmission medium and the setting up of a field trial, while various national firms have been encharged to develop an experimental equipment, working at a high bit rate (800 Mbit/s), which allows the transmission and the bit error rate measurement of two binary streams in a circular waveguide channel at 41 GHz, with QPSK modulation and coherent demodulation.