Measurements of COS in the altitude region between 17 and 30 km were made, using a whole air sampling technique with subsequent gaschromatographic analysis. The data show COS mixing-ratios from about 200 pptv at 17 km decreasing to less than 20 pptv at about 28 km. This behavior is in qualitative agreement with the model-calculations by Turco et al. (1981). From the correlation with CFCl3 and CF2Cl2 the lifetime with respect to removal in the stratosphere is calculated to be 69¿28 years. This corresponds to a sink of between 47 and 112*109 g of COS per year in the stratosphere. Comparing this number to the estimated fluxes needed to sustain the background sulfuric-acid aerosol confirms that most of the non-volcanic aerosol is produced by the oxidation of COS in the stratosphere. ¿ American Geophysical Union 1994