The performance of a ground-based microwave radiometer of new design to be used for remote sensing of the temperature profile of the atmosphere has been tested. It is continuously tunable in the range 52-8-58-8 GHz and has a high absolute accuracy. The radiometer measurements have been analysed with the statistical inversion method and the retrieved profiles have been compared with 28 simultaneous radiosoundings. The r.m.s. difference under clear-sky and cloudy conditions was, on these occasions, less than l-5degK up to 6km and 4km, respectively, less than OdegK up to 8 and 5-5 km, respectively, and less than 3-0degK up to 9 and 7-5 km, respectively. Methods to increase the profiling accuracy are discussed.