We have used a constrained one-dimensional photochemical model to investigate the effect of a potential minor channel of the fast reaction between BrO+OH to produce HBr. There is no direct evidence for this reaction but the analogous yield of HCl from ClO+OH is thought to be about 5%. With only a 1--2% yield of HBr the modelled HBr mixing ratio between 20--30 km increases from around 0.5 parts per 1012 by volume (pptv) to 1--2 pptv. This brings the model into agreement with recent balloon-borne observations of stratospheric HBr. Should BrO+OH produce HBr with around 1--2% yield then this reaction will dominate HBr production between 20--35 km. As the main loss of HBr is reaction with OH this will lead to steady state HBr:BrO partitioning which is independent of other species, and temperature. ¿ 1997 American Geophysical Union