Chlorine activation and chemical ozone destruction is investigated in the Arctic winter 2002--03 using the tracer-tracer correlation technique. Consistent with very low temperatures in the early vortex, strong chlorine activation at 520 K potential temperature was observed already in mid-December 2002 by the MkIV balloon and at 400--500 K in early January 2003 from HALOE satellite measurements. Large column ozone loss was derived inside the outer vortex in January (23 ¿ 9 DU) and substantially greater losses in February (51 ¿ 9 DU) inside the vortex core in 380--550 K. Calculated ozone loss is similar in February in the two completely separated parts of the vortex. Little influence of mixing in of mid-latitude is noticeable after the reunification of the vortex. Further, some ozone loss at lower altitudes likely occurred during March and April consistent with polar stratospheric clouds detected by MIPAS-ENVISAT towards the end of March.