The solubility of HCl in polar stratospheric cloud (PSC) particles plays an important role in the heterogeneous chemistry of the lower polar stratosphere. New labortory studies are reported showing a strong dependence of the HCl solubility on the HNO3 content in ice particles. At 200 K and a partial HCl pressure of 10-6 Torr, the HCl content in NAT is 0.35 mol%, decreasing about a factor of 3 for every 10 fold decrease in the substrate's HNO3 content. At an HCl pressure of 10-7 Torr the content is about 40% of that at 10-6 Torr. HCl dissolved in pure water ice at these partial pressures is less than 0.002 mol%. The surface coverage of HCl on small ice samples was estimated to be about 0.1 monolayer at 10-6 Torr exposure. ¿American Geophysical Union 1991