The Ozone Monitoring Instrument (OMI) is the Dutch-Finnish contribution to the NASA EOS-Aura platform, which was launched in July 2004. OMI is the first of a new generation of UV-Visible space-borne spectrometers that use twodimensional detectors. These detectors enable OMI to daily observe the entire Earth with small ground pixel size (13×24 km² at nadir), which makes this instrument suitable for tropospheric composition research and detection of air pollution at urban scales. The scientific objectives of OMI concern the recovery of the ozone layer, tropospheric pollution, the contribution of tropospheric ozone and aerosols to climate change and changes in surface UV-B. OMI's unique capabilities for measuring important trace gases with daily global coverage and a small footprint, will make a major contribution to our understanding of stratospheric and tropospheric chemistry and climate change along with Aura's other three instruments. In addition to providing data for Aura's prime research objectives, OMI will provide near-real time data for operational agencies in Europe and the United States. In this paper an overview will be presented of several results obtained in the first one-and-a-half year of the OMI instrument on Aura, focused on air quality and validation.