A laser flash photolysis resonance fluorescence technique has been employed to investigate the reactions of atomic chlorine with three alkyl bromides (R-Br) that have been identified as short-Lived atmospheric constituents with significant: ozone depletion potentials (ODPs). Kinetic data are obtained through time-resolved observation of the appearance of atomic bromine that is formed by rapid unimolecular decomposition of radicals generated via abstraction of a beta-hydrogen atom. The following Arrhenius expressions are excellent representations of the temperature dependence of rate coefficients measured for the reactions Cl + CH3CH2Br (eq 1) and Cl + CH3CH2CH2Br (eq 2) over the temperature range 221-436 K (units are 10(-11) cm(3) molecule(-1) s(-1)): k(1)(T) = 3.73 exp(-378/T) and k(2)(T) = 5.14 exp(+21/T). The accuracy (2 sigma) of rate coefficients obtained from the above expressions is estimated to be +/- 15% for k(2)(T) and +15/-25% for k(1) (T) independent of T. For the relatively slow reaction Cl + CH2BrCH2Br (eq 3), a nonlinear in k(3) vs 1/T dependence is observed and contributions to observed kinetics from impurity reactions cannot be ruled out; the following modified Arrhenius expression represents the temperature dependence (244-569 K) of upper-limit rate coefficients that are consistent with the data: k(3)(T) <= 3.2 x 10(-17) T-2 exp(-184/T) cm(3) molecule(-1) s(-1). Comparison of Br fluorescence signal strengths obtained when Cl removal is dominated by reaction with R Br with those obtained when Cl removal is dominated by reaction with Br-2 (unit yield calibration) allows branching ratios for beta-hydrogen abstraction (k(ia)/k(v) i = 1,2) to he evaluated. The following Arrhenius-type expressions are excellent representations of the observed temperature dependences: k(1a)/k(1) = 0.85 exp(-230/T) and k(2a)/k(2) = 0.40 exp(+181/T). The accuracy (2 sigma) of branching ratios obtained from the above expressions is estimated to be +/- 35% for reaction 1 and +/- 25% for reaction 2 independent of T. It appears likely that reactions 1 and 2 play a significant role in limiting the tropospheric lifetime and, therefore, the ODP of CH3CH2Br and CH3CH2CH2Br, respectively.