Vibrational relaxation rate constants for VV energy transfer between a donor and an acceptor molecule in the liquid and gas phases, K L and K G, respectively, are calculated within a kinetic theory framework. The ratio of these quantities and its variation with the vibrational energy transferred (ħΔθ) depend on the way the solvent influences the encounters between the active pair. The analysis assesses the relative importance of correlated and uncorrelated collision sequences on the rate of collision induced vibrational energy transfer. This theory is compared to molecular dynamics calculations on a hard-sphere like system and to the experimental data on small molecules in inert gas solvents. By means of the theory, one finds that (i) the correlated recollisions affect the near resonant (Δθ < 60 cm-1) behaviour of K L/K G; (ii) uncorrelated collisions inherent in Enskog theories describe the higher frequencies; and (iii) the isolated binary collision model is obtained as the infinite frequency, zero energy transfer range limit of the uncorrelated collision model.