Two optical particle counters on the ER-2, together covering a particle size diameter range from 0.1 &mgr;m to 23 &mgr;m, were used to measure the aerosol bulk quantities integral number, aerosol surface and volume, as well as detailed size distributions inside and outside of the polar vortex in the lower stratosphere. While AASE I (Arctic Airborne Stratospheric Expedition (Dec. 88-Feb. 89) was conducted in a period of relative volcanic quiescence, enhancements in aerosol number, surface and volume of factors around 10, 25, and 100 were observed during AASE II (Aug. 91-Mar. 92) due to the eruption of Mt. Pinatubo. The changes in these bulk quantities as well as in the size distributions measured both outside and inside the polar vortex are presented and compared with those obtained in polar stratospheric cloud events (AASE I). Except for a shift towards larger aerosol mixing ratios the general shape of correlograms between the measured N2O and particle mixing ratios remain similar before and after the eruption. Similar correlograms are used to interpret data from vertical profiles inside and outside of the polar vortex. ¿ American Geophysical Union 1993