Products of the gas-phase reaction of Br atoms with NO2 have been quantitatively determined at temperatures between 215 and 300 K in an environmental chamber interfaced to an FT-IR spectrometer. The major product of the reaction (yield > 75%) was found to be the cis isomer of BrONO, which was identified and quantified by means of its N=O stretching fundamental at 1660 cm-(1); this represents the first gas-phase detection of this species. Although rapid thermal decomposition back to Br and NO2 precludes its detection at room temperature (lifetime < 1 s), BrONO was detected at temperatures at and below 263 K. Isomerization of the BrONO to BrNO2 was found to be an important fate of BrONO at low temperatures. The rate coefficient for this process was found to increase with decreasing pressure, indicative of a heterogeneous process. At 700 Torr, this isomerization rate was (0.013 +/- 0.003) s(-1), independent of temperature over the range 218-243 K. Evidence was also obtained for rapid reactions between Br atoms and both BrONO and BrNO2 (10(-10) > k > 10(-11) cm(3) molecule(-1) s(-1)).