Quasiclassical trajectory calculations of vibrational transition rates in Ar+H2 collisions have been carried out. A realistic potential energy surface has been used, and the rates are averaged over rotational-translational distributions at 4500°K. The same transition rates are calculated by eight distorted-wave-based theories which have been used by others for various applications. The present calculations provide a critical test of these theories, especially for high vibrational quantum numbers where data have been scarce. We also discuss dissociation rates, the rotational component of vibrational energy transfer, and a surprisal analysis of the vibrational transition rates.