Bromine oxide (BrO) is proposed to be an important agent for tropospheric ozone depletion, as observed in the high Arctic during springtime. In this paper we report measurements of bromine oxide and ozone by Long Path Differential Optical Absorption Spectroscopy (LPDOAS), 8.6-km light path), performed in April 1992 in Alert (82.3¿N, 62.2 ¿W). BrO mixing ratios were found between the detection limit of about 4 ppt to 17 ppt. Because of the frequently poor visibility conditions, especially during ozone depletion events, long-signal integration times (sometimes more than 24 hours) were needed, and short-time BrO-peaks might have escaped detection. A pure in situ chemical mechanism based on BrO-catalyzed ozone destruction cannot account for the observed complete depletion of ozone at the observed BrO mixing ratios. On the other hand, it can be argued that the maximum time for chemical ozone depletion (by any mechanism) may not be much longer than 1 day. A simple scenario involving a combination of advection, atmospheric dispersion, and BrO-catalyzed chemical ozne destruction is described, which could explain the observed ozone loss. ¿ American Geophysical Union 1994