Total ozone and ozonesonde profiles obtained from Sapporo (43 ¿N) and Tsukuba (36 ¿N), Japan showed significant ozone decreases in 1992 and 1993, coinciding with the large increase of aerosol loading from the Pinatubo eruption. The ozone anomaly in Sapporo was deeper and longer lasting than in Tsukuba, indicating a latitudinal variation. The ozone decrease occurred mainly below 24 km and was most pronounced in winter and spring. In addition, the altitude regions where significant ozone decreases occurred, descended between 1992 and 1994 coincident with the descent of the Pinatubo aerosol layer. Some increase in ozone was seen above 26 km at the two stations in the winter and spring of 1992. These ozone changes are indicative of heterogeneous chemical effects on ozone under perturbed aerosol loading. ¿ American Geophysical Union 1995