The kinetics of the reactions of Br atoms with HO2 and DO2 radicals, Br + HO2 --> HBr + O-2 (1), and Br + DO2 --> DBr + O-2 (3), have been studied by the mass spectrometric discharge-flow method at temperatures between 230 and 355 K and at a total pressure of 1 Torr of helium. The rate coefficients measured under pseudo-first-order conditions in excess Br yield the following Arrhenius expressions: k(1) = (4.9 +/- 0.7) x 10(-12) exp[-(310 +/- 40)/T] and k(3) = (1.9 +/- 0.4) x 10(-12) exp[-(540 +/- 60)/T] cm(3) molecule(-1) s(-1) (uncertainties are 2 sigma). The k(3) value is measured for the first time and that of k(1) is compared with those from previous studies.