BrNO2 was prepared in situ in a static reactor (upsilon = 420 L) by photolyzing Br-2/NO2/N-2 mixtures in the wavelength range 500-700 nm at temperatures between 263 and 294 K. After the lights were switched off, the excess NO was added, and TR and UV spectra were monitored simultaneously as a function of time. From the pseudo-First-order decay of the IR absorption of BrNO2 in the presence of a large excess of NO, the second-order rate constant for reaction 4, BrNO2 + NO => BrNO + NO2, was determined to be k(4) = 2.3 x 10(-12) exp[(-17.8 +/- 2.1) kJ mol(-1)/RT] cm(3)molecule(-1)s(-1) (2 sigma). The measured yields of BrNO were close to 100% (98 +/- 5%). These results suggest that reaction 4 is unimportant as a loss process of BrNO2 under most tropospheric conditions. Additional experiments on the thermal stability of BrNO2 led to an upper limit of 4.0 x 10(-4) s(-1) for its thermal gas-phase decomposition rate constant at 298 K in 1 atm of synthetic air. Finally, the mechanism of the Br + NO2 reaction and the thermochemistry of BrNO2 and BrONO are discussed in light of the results of the present experiments and of previous work from the literature.