Lower stratospheric in situ observations are used to quantify both the accumulated ozone loss and the ozone chemical loss rates in the Arctic polar vortex during the 1999--2000 winter. Multiple long-lived trace gas correlations are used to identify parcels in the inner Arctic vortex whose chemical loss rates are unaffected by extra-vortex intrusions. Ozone-tracer correlations are then used to calculate ozone chemical loss rates. During the late winter the ozone chemical loss rate is found to be -46¿6 (1&sgr;) ppbv/day. By mid-March 2000, the accumulated ozone chemical loss is 58¿4% in the lower stratosphere near 450 K potential temperature (~19 km altitude). ¿ 2001 American Geophysical Union