The absolute rate constant for the reaction O(3P)+HOBr has been measured between T=233 K and 423 K using the discharge-flow kinetic technique coupled to mass spectrometric detection. The value of the rate coefficient at room temperature is (2.5¿0.6)¿10-11 cm3 molecule-1 s-1 and the derived Arrhenius expression is (1.4¿0.5)¿10-10 exp[(-430¿260)/T> cm3 molecule-1 s-1. From these rate data the atmospheric lifetime of HOBr with respect to reaction with O(3P) is about 0.6 h at z=25 km which is comparable to the photolysis lifetime based on recent measurements of the UV cross section for HOBr. Implications for HOBr loss in the stratosphere have been tested using a 1D photochemical box model. With the inclusion of the rate parameters and products for the O+HOBr reaction, calculated concentration profiles of BrO increase by up to 33% around z=35 km. This result indicates that the inclusion of the O+HOBr reaction in global atmospheric chemistry models may have an impact on bromine partitioning in the middle atmosphere. ¿ American Geophysical Union 1995