The Airborne Arctic Stratospheric Expedition (AASE) carried out measurements from January 3 to February 15, 1989. Enhanced levels of chlorine compounds were found in the Arctic stratosphere, and on two single flights ozone decrease of 17% were measured, interpreted as essential features of the Arctic stratosphere, caused by a combined effect of enhanced amounts of chlorine compounds and presence of polar stratospheric clouds. Related model calculations also indicate extended ozone depletion maximizing in late March 1989 and amount to 5--8% in column at 70¿ N. Ground-based ozone measurements, however, show that the most characteristic features during this period are temporal variations and a strong enhancement of ozone, probably due to an extended stratospheric warming. From these measurements it is hard to see any effect of an eventual enhanced burden of stratospheric chlorine, which might show up as an extended and long-lasting decrease of stratospheric ozone, but its eventual existence is masked by the temporal variations. ¿ American Geophysical Union 1994