Both classical and quasiclassical trajectories are used to study the dissociation of noble gas dimers and the transitions between stable and metastable dimers induced by collisions with noble gas atoms. Thermal reaction rates are reported for these processes over a 0.3-3.5 range of reduced temperatures, T* = (k(B)T)/epsilon. Classical and quasiclassical data are compared to assess the importance of quantum effects in the reaction dynamics.