The uptake of HCl on frozen film ice surfaces was studied as a function of temperature and HCl partial pressure (PHCl) in a flow reactor. The temperatures ranged from 205 to 230 K, and PHCl was (0.4-2.0)¿10-6 Torr. The initial uptake coefficients, &ggr;, and the HCl surface coverage are reported. It was observed that the coverage varied from 3.0¿1014 molecules/cm2 at 205 K to 1.0¿1014 molecules/cm2 at 230 K. At 205 K the coverage showed no dependence on PHCl; the average surface coverage was ~(2.0¿0.7)¿1014 molecules/cm2 at saturation. This value is consistent with other studies on similarly prepared ice films. It was found that &ggr;~0.1 at 205 K, but decreased substantially when the temperature increased; however, &ggr; was insensitive to PHCl. ¿ 2001 American Geophysical Union