The episodes when the boundary-layer ozone concentrations in the Arctic drop from the normal 30-40 ppb to less than 3 ppb levels have been found to be associated with high concentrations of 'filterable bromine', and were suggested (Barrie et al., 1988; Bottenheim et al., 1990) to be caused by BrO radicals present in the filterable bromine. This paper describes direct measurements of BrO made in April 1992 during the Polar Sunrise Experiment in the Canadien Arctic, using long-path differential optical absorption spectroscopy (LP-DOAS). A new design of the LP-DOAS spectrometer was employed, based on the principle of Platt and Perner (1983), which uses a holographic flat field grating, a slotted disk as scanning device, and a photomultiplier as a detector. A comparison of ozone concentrations measured with the LP-DOAS with in-situ measurements made by a short-path UV-absorption instrument showed agreement within a few ppb. Measurements for April 1992 indicated BrO concentrations between about 3 ppb to 17 ppb. However, no anticorrelation was found between concentrations of ozone and BrO.