Since January 1995, an ozone line at 110 GHz is observed with a ground-based microwave radiometer at the Bordeaux Observatory, France (45¿N), belonging to the Network for the Detection of Stratospheric Change (NDSC). Ozone profiles from 25 to 75 km are retrieved from the microwave emission spectra using the Optimal Estimation Method. Improvements on the data acquisition process and calibration procedure are presented. A comprehensive comparison with satellite (Halogen Occultation Experiment (HALOE), Microwave Limb Sounder (MLS), and Stratospheric Aerosol and Gas Experiment II (SAGE II)) and ground-based instrument data (microwave radiometer in Bern, Switzerland, lidar at the Observatoire de Haute-Provence, France) is given. The average profiles, using the statistically most significant data sets, deviate not more than 15% in the stratosphere and 30% in the mesosphere. We can thus assert that the Bordeaux radiometer is a well-validated instrument providing consistent and high-quality data.