In this paper we report angular distributions and time-of-flight spectra for the Cl + H2 → HCl + H and Cl + D2 → DCl + D reactions at 5.85 kcal mol-1 and 6.3 and 6.4 kcal mol-1 collision energies, respectively, obtained from high-resolution crossed molecular beam experiments. In addition, quasiclassical trajectory (QCT) and quantum mechanical (QM) dynamical calculations have been carried out for these reactions on the G3 potential energy surface (T. C. Allison et al., J. Phys. Chem., 1996, 100, 13575). Reaction probabilities, integral and differential cross sections have been calculated using the QCT and QM methodologies, and a comparison of these results is presented. The molecular beam results have been simulated using the theoretical calculations, and theory and experiment are in reasonably good agreement.