The interaction of HBr with ice films has been studied in a fast-flow reactor, and the formation of HBr.3H(2)O and HBr.2H(2)O near the ice film surface was determined at 188 K. The existence of the hydrates was further verified by the construction of a low-temperature HBr-ice phase diagram under the experimental conditions. Hydrate formation is a critical process in understanding the higher HBr uptake on ice films and the heterogeneous reaction mechanism involving HBr on the ice surface. The effects of total pressure and ice film thickness on HBr uptake were also investigated. The co-uptake of HBr and HCl showed that the HBr uptake was in general more efficient than that of HCl. This study provides the detailed thermodynamic properties of HBr on ice at the pressure range of 10(-8) - 10(-5) Torr and 180-220 K.