We review the nitrogen dioxide (NO2) data product, which is based on measurements made in the spectral region 415–465 nm by the Ozone Monitoring Instrument (OMI) on the EOS-Aura Satellite. A number of ground- and aircraft-based measurements have been used to validate the data product’s three principal quantities: stratospheric, tropospheric, and total NO2 column densities. It is found that OMI overestimates the stratospheric column by about 10%, and underestimates both the total and tropospheric columns by 15 − 30%. Because some of the techniques have not themselves been validated, and because of problems inherent in comparing point measurements from the ground to large area averaged satellite measurements, and because some of the measurements have been made only over short periods of time, validation results are sometimes only qualitative.