The geometries, vibrational spectra, and relative energetics of the formation of OBrO radicals during the reaction between hydroxyl radicals and HOBrO have been examined by using various ab initio methods. The heat of reaction for the formation of OBrO radicals from the reaction between HO and HOBrO is -37.0 kcal mol(-1), while the energy barrier for activation of the reaction is 3.9 kcal mol-1. Results suggest that the reaction between HO and HOBrO species could serve as a minor source of OBrO radicals in the atmosphere.