The collisional deactivation of H2O by Ar has been studied by using classical trajectory calculations, with an initial vibrational energy of 50, 75, and 100 kcal/mol, rotational temperatures in the range 0-10 000 K, and translational energies corresponding to the Boltzmann distribution at 298 K. Some results at 1000 K are also presented. The effect of internal energy on the first and second moments is examined. Increasing the initial vibrational energy enhances the intermolecular relaxation. However, the rotational temperature has a complex effect. The results are analyzed using a cumulative probability distribution of the amount of energy transferred in deactivating collisions, Q(Delta E), obtained by direct count of the number of trajectories that transfer an amount of energy equal to or greater than a certain amount, Delta E. The transition probability for energy transfer, P(E',E), is then obtained by differentiation of the cumulative function. Scaling of Q(Delta E) in terms of the mean down energy lost in deactivating collisions, [Delta E](d), for each group of trajectories, results in a unique distribution. This function then allows us to obtain a global P(E',E) which depends on [Delta E](d) as a single parameter.