The evolution of ozone (O3) observed by the Microwave Limb Sounder on board the Upper Atmosphere Research Satellite is described for 14 August through 20 September 1992, in relation to the polar vortex. The development of an ozone hole is observed in column O3, and a corresponding decrease is seen in O3 mixing ratio in the polar lower stratosphere, consistent with chemical destruction. The observations also suggest that poleward transport associated with episodes of strong planetary wave activity is important in increasing O3 in the mid-stratosphere. ¿ American Geophysical Union 1993