Measurements with an airborne lidar performed during the Arctic winter 1994/95 show, that the ozone mixing ratio declined by about 50% throughout the polar vortex in the period from the beginning of February to mid of March in a sharp defined altitude band from 420 K to 520 K potential temperature. The simultaneous detection of the stratospheric aerosol density provides evidence that this depletion was not caused by dynamical processes but by chemical reactions. ¿ American Geophysical Union 1996