Evening twilight sky spectra in the region 437–451 nm obtained from the Aeronomy Observatory, University of Calgary (50.08, 114.13°W) in the period May 1978–April 1979 have been analyzed to determine the vertical column abundance of stratospheric NO2. The analysis shows approximately a three-fold seasonal change in the NO2 column abundance with a maximum value in summer of 5.6 × 1015 cm−2.