Following the arrival of Pinatubo volcanic aerosols, significant decreases in NO2 column amount were observed at Moshiri, Japan (44 ¿N, 142 ¿E). A slight decrease started in September 1991 and reductions of more than 20% have been seen since January 1992. The reduction was largest in April 1992 when NO2 amounts were about 50% lower than observed in April 1991. Between May 1992 and January 1993, the reduction has been getting smaller, however until October 1992, about 35 to 20% lower NO2 amounts were observed. At southern mid-latitudes, a clear decrease in NO2 started in August 1991 [Johnston et al., 1992>. Aerosol data obtained from lidar measurements and the SAGE II satellite instrument show that the observed major reductions in NO2 in the both hemispheres generally correspond to the arrival of volcanic aerosols above 25 km. ¿ American Geophysical Union 1993