The coupling between vibrational relaxation and dissociation is discussed. A model for computations of dissociation behind strong shock waves is presented. It is shown that the loss of vibrational energy during dissociation introduces an inverse temperature dependence into the observed dissociation rate of O2 between 4000 and 8000K. Changing the model so that dissociation from higher vibrational levels is enhanced results in a dissociation-incubation time immediately behind the shock. The vibrational-energy distribution behind the shock is calculated, and shown to depart considerably from a Boltzmann distribution. The molecular model, which uses a Boltzmann distribution, is shown to give the same result as the non-Boltzmann model for both the nonequilibrium dissociation rate and the dissociation incubation time. (Author).