Atmospheric NO2 content data obtained from regular ground-based measurements of solar IR radiation in the St. Petersburg region using a spectrometer with a high spectral resolution are analyzed. The absorption spectra of the NO2 multiplet in the vicinity of ∼2915 cm−1 allow one to obtain data on variations in the stratospheric total content of NO2 in 2009–2011. The accuracy of these data is estimated from their comparison with data obtained from independent ground-based and satellite measurements. The parameters of the seasonal cycle of the stratospheric content of NO2 are estimated. The body of data accumulated during these measurements in the IR region made it possible to isolate the component of a daytime photochemical increase in the stratospheric content of NO2 and estimate its rate.