Results of microwave studies of stratospheric ozone above ≈20 km in high latitudes in the years 1986--1990 are presented. Measurements were performed with a ground-based spectral heterodyne receiver. The technique is based on the measurements of atmospheric ozone emission in lines of rotational transitions corresponding to frequencies of about 102 and 142 GHz. The main result of the investigations is the detection of rather strong stratospheric ozone variability above ≈20 km. The characteristic timescales of these variations extend from a few hours in some periods of observation to a few days, weeks, or months. The latter may be considered as seasonal variations. ¿ American Geophysical Union 1994