Observations of nitrogen dioxide have been performed at the International Scientific Station at the Jungfraujoch (46.5°N, 8.0°E) during the winters 1990–1991 and 1991–1992. Vertical abundances of NO2 were obtained by measuring the scattered sunlight at the zenith, during sunset and sunrise, using the differential absorption method in the visible spectrum. The comparison between the two winters shows a NO2 reduction of 15% in March–May 1992, following the eruption of Mt. Pinatubo. This decrease is likely to be due to heterogeneous reactions on the volcanic aerosols converting N2O5 to HNO3. Radiative interferences on ground‐based visible absorption measurements of NO2 caused by the enhanced aerosol layer are considered to be negligible (Perliski and Solomon, 1992). The results are discussed with respect to measurements made at Lauder, New Zealand (45°S, 170°E) and published by Johnston et al. (1992).