Observations made by the High Resolution Doppler Imager (HRDI) onboard the Upper Atmosphere Research Satellite (UARS) of molecular oxygen Atmospheric band dayglow and temperature are used to infer ozone mixing ratios in the mesosphere and lower thermosphere. The retrieval relies on the fact that a significant portion of the dayglow originates from ozone photolysis. Observations cover up to 72¿ in latitude and an altitude range of 65--97 km, with a vertical resolution of 2.5 km. Error analysis shows that measurement errors in observed ozone volume mixing ratios are typically between 0.04 and 0.1 parts per million, although systematic errors may be larger. Measurements show good agreement with previous observations and with other UARS instruments. A unique feature of the HRDI mesospheric ozone data set is that all daylight local times are sampled, which allows resolution of large diurnal variations throughout the mesosphere. Dynamical signatures are clearly seen in the distribution of ozone, which indicates that vertical advection of atomic oxygen by the solar diurnal tide plays an important role in determining ozone concentrations.