Spectrometric measurements of nitrogen dioxide by the observation of the sunlight absorption in the visible range, from a balloon executing large vertical excursions, were performed along a complete day on September 1979 at 43¿N, 00¿W. The instrument and the data processing method developed allow a detection limit of NO2 along the line of sight of 4¿1015 mol cm-2. The results show in the lower stratosphere an NO2 diurnal variation with a maximum around noon. Above 22 km, the vertical column density varies from 2.4¿0.7¿1015 mol cm-2 at 06:15 to 10.0¿2.8¿1015 mol cm-2 at 11:20 and 6.4¿1.4¿1015 mol cm-2 at 17:00. At noon, the mean concentration between 22 and 33.5 km is 8.7¿3.2¿109 mol cm-3 which corresponds to a mixing ratio of 13.1¿4.8 ppbv. By comparison with a solar spectrum obtained at 33 km, ground observations made the day before the flight around 13:00 allow a direct measurement of the total atmospheric NO2 column density: 24¿3¿1015 mol cm-2.