The effect of the air quality ensuring measures for the Beijing 2008 Olympic Games in reducing air pollution during the game period is assessed using the tropospheric NO2 column density retrieved from Ozone Monitoring Instrument onboard AURA satel- lite. The basic method of the assessment is the comparison of the NO2 column densities during the game period with that during the corresponding period of 2005?2007 for the Beijing area, and the comparison among Beijing and neighbouring cities Tianjin and Tangsha...