This paper focuses on the recovery of chlorine reservoir species in the lower stratosphere in late Antarctic spring. The investigations are based on measurements from the Halogen Occultation Experiment (HALOE) on board the Upper Atmosphere Research Satellite (UARS) and calculations by the Mainz photochemical box model and the NASA Langley Research Center trajectory model. During late Antarctic spring 1994, HALOE observed high HCl mixing ratios up to 2.7 ppbv at 20 km altitude in the ozone-depleted air inside the polar vortex. These values correspond approximately to the sum of all available inorganic chlorine species. In the preceding period of chlorine activation on polar stratospheric clouds (PSCs), the observed HCl mixing ratios in some cases were below 0.3 ppbv. This indicates a fast conversion of active chlorine species into the form of HCl after PSCs disappear with increasing stratospheric temperatures. Box model calculations are presented that assess the rate of HCl increase in late spring when heterogeneous chemistry on polar stratospheric clouds becomes insignificant. The calculations were performed along Lagrangian trajectories starting from HALOE measurements in September 1994. Sensitivity calculations are presented regarding uncertainties in input parameters of the calculations. In the vortex edge region, calculated HCl increase rates are significantly lower compared with HALOE observations. Introducing additional HCl-yielding branches of the reactions of ClO with OH and HO2 helps to reduce this discrepancy.¿ 1997 American Geophysical Union