Modelling surface adsorption of HCl on type II PSC's, we have performed computer simulations of adsorption of HCl on single crystal ice. For stratospheric conditions, the maximum surface coverage of ice by HCl is calculated to be 10-7 monolayer. This value was obtained by taking surface disorder into account. It is much too low for the reaction of HCl with chloronitrate to proceed rapidly on ordinary ice in one step. The calculated value of the surface coverage is much lower than recent experimental values for the uptake of HCl by polycrystalline ice, and the validity of the interpretation of the uptake of HCl by polycrystalline ice as being due to surface adsorption is questioned. ¿ American Geophysical Union 1992