The title reactions were studied using cavity ring-down spectroscopy in 100 Torr of N-2 diluent at 278-333 K. The equilibrium constant and rates of the forward and reverse reactions of the Br + DMS reversible arrow Br-DMS equilibrium were determined to be K = (4.1 +/- 0.3) x 10(-15) cm(3) molecule(-1), k(forward) = (5.0 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1), and k(backward) = (1.2 +/- 0.2) x 10(4) s(-1) at 300 K in 100 Torr of N-2. The absorption cross section of the Br-DMS adduct at 338.3 nm was sigma = (1.2 +/- 0.2) x 10(-17) cm(2) molecule(-1). An upper limit of k < 1 x 10(-18) cm(3) molecule(-1) s(-1) was established for the reaction Of O-2 with the Br-DMS adduct. The kinetics of the reaction of BrO with DMS were well described by the Arrhenius expression k = (1.3 +/-0.1) x 10(-14) exp[(1033 +/- 265)/T] cm(3) molecule(-1) s(-1) (k = 4.2 x 10(-13) cm(3) molecule(-1), s(-1) at 298 K). The uncertainties are 2 standard deviations from regression analyses.