HBr uptake an thin ice films was examined using laser-induced thermal desorption (LITD), temperature programmed desorption (TPD) and Fourier transform infrared (FTIR) spectroscopy techniques. LITD was used to determine the uptake coefficient in situ during low HBr exposures as a function of HBr pressure and ice film temperature. The HBr uptake coefficient on ice was gamma = 0.61 +/- 0.06 at 140 K and gamma = 0.24 +/- 0.05 at 100 K at low HBr coverages for HBr pressures ranging from 3 x 10(-8) to 1.4 x 10(-7) Torr. TPD and FTIR were used to examine HBr uptake on ice at higher HBr exposures. TPD studies observed that thin ice films exposed to HBr at 140 K saturated with HBr after large exposures and formed an HBr hydrate with an H2O:HBr ratio of similar to3.6.1. FTIR measurements monitored the development of the H3O+ bending vibration Versus HBr exposure on ice. Saturation of the integrated absorbance for this H3O+ bending vibration was observed after large HBr exposures. The uptake of HBr on ice also had a profound effect on H2O desorption from ice. H2O desorbed at higher temperatures in the presence of HBr. The zero-order kinetics for H2O desorption from pure ice were E-d = 13.4 kcal mol(-1) and nu (0) = 1.9 x 10(32) cm(-2) s(-1). The zero-order kinetics for H2O desorption from the HBr hydrate fanned after saturation HBr exposures were E-d = 10.6 kcal mol(-1) and nu (0) = 6.3 x 10(27) cm(-2) s(-1).