A dynamics study of the reaction Ar + HCN --> Ar + H + CN for a wide range of initial vibrational and translational energies is reported. All calculations have been carried out with the quasiclassical trajectory method and a realistic potential energy surface for ArHCN. An attempt is made to reproduce the thermal rate coefficient for the reaction. Agreement with experiment is found to be good, and the limitations of the approach are stressed. A brief analysis of rotational effects, energy transfer, and unimolecular dissociation of highly excited HCN* molecules is also presented.