|A good quantitative understanding of chemical ozone loss in the polar regions is necessary to predict reliably the future of the ozone layer. In the Arctic, ozone loss rates have been determined by a number of approaches during the past tenures. Recent comparisons with model calculations give reason to assume that threat of rapid ozone loss in the Arctic is not yet understood quantitatively under certain conditions. To further investigate the situation, models and observations have to be compared under a broader spectrum of meteorological conditions. Therefore we propose high precision measurements of chemical ozone loss rates not only in the Arctic but also in the Antarctic. The results will be compared with several state-of-the-art 3D chemical transport models and photochemical box models. The aim is to determine whether deficiencies exist and identify possible reasons. This may contribute to the development of better models for predictions.